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  • 301.
    Krysander, Mattias
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nyberg, Mattias
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik.
    An Efficient Algorithm for Finding Minimal Overconstrained Subsystems for Model-Based Diagnosis2008Inngår i: IEEE transactions on systems, man and cybernetics. Part A. Systems and humans, ISSN 1083-4427, E-ISSN 1558-2426, Vol. 38, nr 1, s. 197-206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In model based diagnosis, the diagnostic system construction is based on a model of the technical system to be diagnosed. To handle large differential algebraic models and to achieve fault isolation, a common strategy is to pick out small over-constrained parts of the model and to test these separately against measured signals. A new algorithm for computing all minimal over-constrained sub-systems in a model is proposed. For complexity comparison, previous algorithms are recalled. It is shown that the time complexity under certain conditions is much better for the new algorithm. This is illustrated using a truck engine model.

  • 302.
    Krysander, Mattias
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Nyberg, Mattias
    Linköpings universitet, Institutionen för systemteknik.
    An Efficient Algorithm for Finding Over-constrained Sub-systems for Construction of Diagnostic Tests2005Inngår i: 16th International Workshop on Principles of Diagnosis DX-05,2005, Pacific Grove, California, USA, 2005, s. 55-60Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a new algorithm for computing all minimal over-constrained sub-systems in a structural model is proposed. To handle large differential algebraic models in diagnosis, systematic structural approaches to find testable sub-systems have been suggested. It is shown how the algorithm can be incorporated and improve some of them. Previous algorithms are recalled and it is shown that the new algorithm is 14000 times faster when applied to a Scania truck engine model.

  • 303.
    Källkvist, Kurt
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Fuel Pressure Modelling in a Common-Rail Direct Injection System2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The fuel pressure is one of the central control variables of a modern common-rail injection system. It influences the generation of nitrous oxide and particulate matter emissions, the brake specific fuel consumption of the engine and the power consumption of the fuel pump. Accurate control of the fuel pressure and reliable diagnostics of the fuel system are therefore crucial components of the engine management system. In order to develop for example control or diagnostics algorithms and aid in the understanding of how hardware changes affect the system, a simulation model of the system is desirable. 

    A Simulink model of the XPI (Xtra high Pressure Injection) system developed by Scania and Cummins is developed. Unlike the previous models of the system available, the new model is geared towards fast simulations by modelling only the mean flow and pressure characteristics of the system, instead of the momentary flow and pressure variations as the engine rotates. The model is built using a modular approach where each module represents a physical component of the system. The modules themselves are based to a large extent on the physical properties of the components involved, making the model of the system adaptable to different hardware configurations whilst also being easy to understand and modify.

  • 304.
    Lannerhed, Petter
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Structural Diagnosis Implementation of Dymola Models using Matlab Fault Diagnosis Toolbox2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Models are of great interest in many fields of engineering as they enable prediction of a systems behaviour, given an initial mode of the system. However, in the field of model-based diagnosis the models are used in a reverse manner, as they are combined with the observations of the systems behaviour in order to estimate the system mode. This thesis describes computation of diagnostic systems based on models implemented in Dymola. Dymola is a program that uses the language Modelica. The Dymola models are translated to Matlab, where an application called Fault Diagnosis Toolbox, FDT is applied. The FDT has functionality for pinpointing minimal overdetermined sets of equations, MSOs, which is developed further in this thesis. It is shown that the implemented algorithm has exponential time complexity with regards to what level the system is overdetermined,also known as the degree of redundancy. The MSOs are used to generate residuals, which are functions that are equal to zero given that the system is fault-free. Residual generation in Dymola is added to the original methods of the FDT andthe results of the Dymola methods are compared to the original FDT methods, when given identical data. Based on these tests it is concluded that adding the Dymola methods to the FDT results in higher accuracy, as well as a new way tocompute optimal observer gain. The FDT methods are applied to 2 models, one model is based on a system ofJAS 39 Gripen; SECS, which stands for Secondary Enviromental Control System. Also, applications are made on a simpler model; a Two Tank System. It is validated that the computational properties of the developed methods in Dymolaand Matlab differs and that it therefore exists benefits of adding the Dymola implementations to the current FDT methods. Furthermore, the investigation of the potential isolability based on the current setup of sensors in SECS shows that full isolability is achievable by adding 2 mass flow sensors, and that the isolability is not limited by causality constraints. One of the found MSOs is solvable in Dymola when given data from a fault-free simulation. However, if the simulation is not fault-free, the same MSO results in a singular equation system. By utilizing MSOs that had no reaction to any modelled faults, certain non-monitored faults is isolated from the monitored ones and therefore the risk of false alarms is reduced. Some residuals are generated as observers, and a new method for constructing observers is found during the thesis by using Lannerheds theorem in combination with Pontryagin’s Minimum Priniple. This method enables evaluation of observer based residuals in Dymola without any selection of a specific operating point, as well as evaluation of observers based on high-index Differential Algebraic Equations, DAEs. The method also results in completely different behaviourof the estimation error compared to the method that is already implemented inthe FDT. For example, one of the new observer-implementations achieves both an estimation error that converges faster towards zero when no faults are implementedin the monitored system, and a sharper reaction to implemented faults.

  • 305.
    Larsson, Camilla
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Reduction of oil pump losses in automatic transmissions2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the vehicle industry it is of great interest to reduce the emissions and lower the fuel consumption.Up to now a lot of effort has been put into increasing the efficiency of the engine,but it starts to get expensive to keep improving the engine. In this master thesis the transmissionand especially the oil supply to the transmission is investigated.

    An example of how the requirements of an oil pump can be decided is described. Knowingthe requirements different pumps may be adapted to meet the demands. The gear pumpused today is compared with a variable displacement pump and an electric pump. The gearpump is not possible to control, but the other two are. A few simple control strategies areintroduced. The strategies are implemented and the three pumps are used in the same drivecycle. It is shown that it is possible to reduce the energy that the pump requires if it isreplaced by a variable vane pump or an electric pump.

  • 306.
    Larsson, Emil
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Diagnosis and Supervision of Industrial Gas Turbines2012Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Monitoring of industrial gas turbines is of vital importance, since it gives valuable information for the customer about maintenance, performance, and process health. The performance of an industrial gas turbine degrades gradually due to factors such as environment air pollution, fuel content, and ageing to mention some of the degradation factors. The compressor in the gas turbine is especially vulnerable against contaminants in the air since these particles are stuck at the rotor and stator surface. The loss in compressor performance, due to fouling, can partially be restored by an on-line/off-line compressor wash. If the actual health state of the gas turbine is known, it is possible to efficiently plan the service and maintenance and thereby reduce the environmental impact and the fuel cost for the customer.

    A thermodynamic gas turbine modeling package, called GTLib, is developed in the equation-based object-oriented modeling language Modelica. Using the GTLib package, a gas turbine model can be constructed. The gas turbine model can be used for performance calculation and as a base when diagnosis tests are generated. These tests can be used in a diagnosis and supervision system to detect compressor fouling and abrupt sensor faults. One of the benefits with using GTLib is the ability to model a lean stoichiometric combustion at different air/fuel ratio. Using the air/fuel ratio concept, an arbitrary number of gas species in the in-coming air can be considered. The number of equations is reduced if the air/fuel ratio concept is considered instead of modeling each gas species separately. The difference in the number of equations is significant if many gas species are considered.

    When the gas turbine components deteriorate, a mismatch between the nominal performance model and the measurements increase. To handle this, the gas turbine model is augmented with a number of estimation parameters. These estimation parameters are used to detect slow deterioration in the gas turbine components and are estimated with a Constant Gain Extended Kalman Filter (CGEKF). The state estimator is chosen using structural methods before an index reduction of the model is performed. Experimental data is investigated and it is shown that the performance degradation due to compressor fouling can be estimated. After the compressor is washed, the performance of the compressor is partially restored. An abrupt sensor fault of 1% of the nominal value is introduced in the discharge temperature of the compressor. The sensor fault can be detected using the CUSUM algorithm for change detection.

    Finally, the overall thesis contribution is the calculation chain from a simulation model used for performance calculation to a number of test quantities used in a diagnosis and supervision system. Since the considered gas turbine model is a large non-linear DAE model that has unobservable state variables, the test construction procedure is automatically performed with developed parsers.

  • 307.
    Larsson, Emil
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Model Based Diagnosis and Supervision of Industrial Gas Turbines2014Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Supervision of performance in gas turbine applications is important in order to achieve: (i) reliable operations, (ii) low heat stress in components, (iii) low fuel consumption, and (iv) efficient overhaul and maintenance. To obtain good diagnosis performance it is important to have tests which are based on models with high accuracy. A main contribution of the thesis is a systematic design procedure to construct a fault detection and isolation (FDI) system which is based on complex nonlinear models.These models are preliminary used for simulation and performance evaluations. Thus, is it possible to use thesemodels also in the FDI-system and whichmodel parts are necessary to consider in the test design? To fulfill the requirement of an automated design procedure, a thermodynamic gas turbine package GTLib is developed. Using the GTLib framework, a gas turbine diagnosismodel is constructed where component deterioration is introduced. In the design of the test quantities, equations from the developed diagnosis models are carefully selected.These equations are then used to implement a Constant Gain Extended Kalman filter (CGEKF) based test quantity.The number of equations and variables which the test quantity is based on is significantly reduced compared to the original reference model.The test quantity is used in the FDI-system to supervise the performance and the turbine inlet temperature which is used in the controller. An evaluation is performed using experimental data from a gas turbine site.The case study shows that the designed FDI-system can be used when the decision about a compressor wash is taken. When the FDI-system is augmented with more test quantities it is possible to diagnose sensor and actuator faults at the same time the performance is supervised. Slow varying sensor and actuator bias faults are difficult diagnose since they appear in a similar manner as the performance deterioration, but the FDI-system has the ability to detect these faults. Finally, the proposed model based design procedure can be considered when an FDI-system of an industrial gas turbine is constructed.

  • 308.
    Larsson, Emil
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Fault Isolation for an Industrial Gas Turbine with a Model-Based Diagnosis Approach2010Inngår i: Proceedings of ASME Turbo Expo, ASME Press, 2010, s. 89-98Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Model based diagnosis and supervision of industrial gas turbines are studied. Monitoring of an industrial gas turbine is important as it gives valuable information for the customer about service performance and process health. The overall objective of the paper is to develop a systematic procedure for modelling and design of a model based diagnosis system, where each step in the process can be automated and implemented using available software tools. A new Modelica gas media library is developed, resulting in a significant model size reduction compared to if standard Modelica components are used. A systematic method is developed that, based on the diagnosis model, extracts relevant parts of the model and transforms it into a form suitable for standard observer design techniques. This method involves techniques from simulation of DAE models and a model reduction step. The size of the final diagnosis model is 20% of the original model size. Combining the modeling results with fault isolation techniques, simultaneous isolation of sensor faults and fault tolerant health parameter estimation is achieved.

  • 309.
    Larsson, Emil
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Åslund, Jan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Fault Tolerant Supervision of an Industrial Gas Turbine2013Inngår i: Proceedings of ASME Turbo Expo, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Supervision of the performance of an industrial gas turbine is important since it gives valuable information of the process health and makes efficient determination of compressor wash intervals possible. Slowly varying sensor faults can easily be misinterpreted as performance degradations and result in an unnecessary compressor wash. Here, a diagnostic algorithm is carefully combined with non-linear state observers to achieve fault tolerant performance estimation. The proposed approach is evaluated in an experimental case study with six months of measurement data from a gas turbine site. The investigation shows that faults in all gas path instrumentation sensors are detectable and isolable. A key result of the case study is the ability to detect and isolate a slowly varying sensor fault in the discharge temperature sensor after the compressor. The fault is detected and isolated before the wash condition of the compressor is triggered, resulting in fault tolerant estimation of compressor health parameters.charge temperature sensor after the compressor. The fault is detected and isolated before the wash condition of the compressor is triggered, resulting in fault tolerant estimation of compressor health parameters.

  • 310.
    Larsson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Gas Turbine Modeling for Diagnosis and Control2014Inngår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 136, nr 7, s. 071601-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The supervision of performance in gas turbine applications is crucial in order to achieve: (i) reliable operations, (ii) low heat stress in components, (iii) low fuel consumption, and (iv) efficient overhaul and maintenance. To obtain a good diagnosis of performance it is important to have tests which are based on models with high accuracy. A main contribution is a systematic design procedure to construct a fault detection and isolation (FDI) system for complex nonlinear models. To fulfill the requirement of an automated design procedure, a thermodynamic gas turbine package (GTLib) is developed. Using the GTLib framework, a gas turbine diagnosis model is constructed where component deterioration is introduced. In the design of the test quantities, equations from the developed diagnosis model are carefully selected. These equations are then used to implement a constant gain extended Kalman filter (CGEKF)-based test quantity. The test quantity is used in the FDI-system to supervise the performance and in the controller to estimate the flame temperature. An evaluation is performed using experimental data from a gas turbine site. The case study shows that the designed FDI-system can be used when the decision about a compressor wash is taken. Thus, the proposed model-based design procedure can be considered when an FDI-system of an industrial gas turbine is constructed.

  • 311.
    Larsson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Health Monitoring in an Industrial Gas Turbine Application by Using Model Based Diagnosis Techniques2012Inngår i: Proceedings of ASME Turbo Expo, 2011, GT2011, June 6-10, 2011, Vancouver, British Columbia, Canada, ASME Digital Collection , 2012, Vol. 3, s. 487-495, artikkel-id GT2011-46825Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Monitoring of an industrial gas turbine is important since it gives valuable information for the customer about maintenance, performance and process health. The objective of the paper is to develop a monitoring system for an industrial gas turbine application with a model based diagnosis approach. A constant gain extended Kalman observer is developed. The observer compensates for different ambient conditions such as pressure, temperature and relative humidity, due to the amount of water in the atmosphere. The developed observer, extended with seven health parameters, is automatically constructed from the diagnosis model. These health parameters shall capture deviations in some of the gas path performance parameters such as efficiency, mass flow, turbine inlet area and head loss. The constructed observer is evaluated through a simulation study where the ambient conditions are changed. The considered observer capture the change in different ambient conditions nearly perfect. An observer that does not compensate for different ambient conditions gives an error for about 1–2% for the considered health parameters for the given test case. The constructed observer is also evaluated on measurement data from a mechanical drive site. A degradation in efficiency and mass flow for the compressor due to fouling can be seen in the estimations. After the compressor wash is performed, the degradations for the compressor are partially restored by about 2% which can be seen in the considered health parameters.

  • 312.
    Larsson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Health Monitoring in an Industrial Gas Turbine Application by Using Model Based Diagnosis Techniques2011Inngår i: Proceedings of ASME Turbo Expo 2011, GT2011, June 6-10, 2011, Vancouver, British Columbia, Canada, ASME Digital Collection , 2011, Vol. 3, s. 487-495, artikkel-id GT2011-46825Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Monitoring of an industrial gas turbine is important since it gives valuable information for the customer about maintenance, performance and process health. The objective of the paper is to develop a monitoring system for an industrial gas turbine application with a model based diagnosis approach. A constant gain extended Kalman observer is developed. The observer compensates for different ambient conditions such as pressure, temperature and relative humidity, due to the amount of water in the atmosphere. The developed observer, extended with seven health parameters, is automatically constructed from the diagnosis model. These health parameters shall capture deviations in some of the gas path performance parameters such as efficiency, mass flow, turbine inlet area and head loss. The constructed observer is evaluated through a simulation study where the ambient conditions are changed. The considered observer capture the change in different ambient conditions nearly perfect. An observer that does not compensate for different ambient conditions gives an error for about 1-2 % for the considered health parameters for the given test case. The constructed observer is also evaluated on measurement data from a mechanical drive site. A degradation in efficiency and mass flow for the compressor due to fouling can be seen in the estimations. After the compressor wash is performed, the degradations for the compressor are partially restored by about 2 % which can be seen in the considered health parameters.

  • 313.
    Larsson, Martin
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Electric Motors for Vehicle Propulsion2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This work is intended to contribute with knowledge to the area of electic motorsfor propulsion in the vehicle industry. This is done by first studying the differentelectric motors available, the motors suitable for vehicle propulsion are then dividedinto four different types to be studied separately. These four types are thedirect current, induction, permanent magnet and switched reluctance motors. Thedesign and construction are then studied to understand how the different typesdiffer from each other and which differences that are of importance when it comesto vehicle propulsion. Since the amount of available data about different electricmotors turned out to be small a tool was developed to use for collecting data fromthe sources available which can be for instance product sheets or articles with informationabout electric motors. This tool was then used to collect data that wasused to create models for the different motor types. The created motor models foreach motor type could then be used for simulating vehicles to investigate how thespecific motor is suited for different vehicles and applications. The work also containsa summary of different electric motor comparison studies which makes it agood source of information during motor type selection in the process of designingan electric vehicle.

  • 314.
    Larsén, Nils
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Real-Time Calibration of the Steering Wheel Angle Sensor2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A stationary or temporary offset in the steering system of a vehicle can result in functions, relying on the steering wheel angle, performing poorly. Due to the wide range of different vehicle configurations at Scania CV, all sensors with relevant information regarding vehicle direction are not available on all vehicles. By using a statistical approach, including common sensors installed on the vehicle, a conceptual algorithm calibrating the Steering Wheel Angle Sensor offset in real- time has been developed. The algorithm is simple and relies on the assumption that a vehicle is driving straight ahead most of the time above a certain minimum vehicle speed, thus the most frequent steering wheel angle is the straight ahead angle. The algorithm is only active above the certain minimum vehicle speed and consists of two moving windows comprising steering wheel angle samples in which the calculations are performed. The results show that the algorithm is able to detect offsets with a short calibration time. Storage of samples is required but no vehicle specific parameters are needed. 

  • 315.
    Lee, Chih Feng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Khong, Sei Zhen
    Department of Automatic Control, Lund University.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Krysander, Mattias
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    An extremum seeking approach to parameterised loop-shaping control design2014Inngår i: Proceedings of The 19th World Congress of the International Federation of Automatic Control (IFAC 2014), Elsevier, 2014, Vol. 47, nr 3, s. 10251-10256Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An approach to loop-shaping feedback control design in the frequency domain via extremum seeking is proposed. Both plants and controllers are linear time-invariant systems of possibly infinite dimension. The controller is assumed to be dependent on a finite number of parameters. Discrete-time global extremum seeking algorithms are employed to minimise the difference between the desired loop shape and the estimate of the present loop shape by fine-tuning the controller parameters within a sampled-data framework. The sampling period plays an important role in guaranteeing global practical convergence to the optimum. A case study on PID control tuning is presented to demonstrate the applicability of the proposed method.

  • 316.
    Lee, Chih Feng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Manzie, Chris
    University of Melbourne, Australia.
    Active Brake Judder Attenuation Using an Electromechanical Brake-by-Wire System2016Inngår i: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, Vol. 21, nr 6, s. 2964-2976Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Brake judder is an undesirable phenomenon in passenger vehicles whereby disk thickness variations lead to brake torque variations (BTVs) during light braking events with a consequence of reduced braking performance and driver satisfaction. Most solutions involve passive approaches; however, in this study, a novel active brake judder attenuation strategy utilizing the capabilities of a prototype electromechanical brake (EMB) is proposed. Two attenuation algorithms with different sensor requirements are presented, where compensating clamp force commands are generated to cancel the judder causing BTV arises during light braking. The first approach is founded on the linear parameter-varying (LPV) control structure, which is designed using the output regulation theory and scheduled using wheel angular speed and acceleration. The second approach examines the adaptive feedforward compensation, where the compensator is scheduled using wheel angular position, speed, and acceleration. Experimental investigations showed favorable results for the LPV compensator, albeit with high sampling rate requirements. On the other hand, the adaptive compensator demonstrated lower sampling rate requirements with better BTV attenuation, but required wheel position measurements. These results highlight the applicability of EMBin judder reduction and the advantage of having wheel measurements.

  • 317.
    Lee, Chih Feng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Manzie, Chris
    Active Brake Torque Variation Compensation with Speed Scheduling of an Electromechanical Brake2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An approach to attenuate the brake judder actively is proposed. The proposed judder compensation algorithm generates a clamp force command that attenuates the judder inducing brake torque variation. An electromechanical brake with high-bandwidth closed-loop clamp force tracking performance is utilised to follow the generated command, where the judder is compensated at its source. Experimental results are presented and the compensator is validated over fixed and varying wheel speeds with significant judder attenuation demonstrated.

  • 318.
    Lee, Chih Feng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Savitski, Dzmitry
    Ilmenau Technical University.
    Manzie, Chris
    University of Melbourne.
    Ivanov, Valentin
    Ilmenau Technical University.
    Active Brake Judder Compensation Using an Electro-Hydraulic Brake System2015Inngår i: SAE International Journal of Commercial Vehicles, ISSN 1946-391X, E-ISSN 1946-3928, Vol. 8, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Geometric imperfections on brake rotor surface are well-known for causing periodic variations in brake torque during braking. This leads to brake judder, where vibrations are felt in the brake pedal, vehicle floor and/or steering wheel. Existing solutions to address judder often involve multiple phases of component design, extensive testing and improvement of manufacturing procedures, leading to the increase in development cost. To address this issue, active brake torque variation (BTV) compensation has been proposed for an electromechanical brake (EMB). The proposed compensator takes advantage of the EMB’s powerful actuator, reasonably rigid transmission unit and high bandwidth tracking performance in achieving judder reduction. In a similar vein, recent advancements in hydraulic system design and control have improved the performance of hydraulic brakes on a par with the EMB, therefore invoking the possibility of incorporating the BTV compensation feature of the EMB within hydraulic brake hardware. In this paper, the typical characteristics of electromechanical and electro-hydraulic brake systems are presented. Based on the experimental results, the feasibility of active BTV compensation on the electro-hydraulic brake (EHB) systems is discussed. Furthermore, a BTV compensation algorithm designed for the EMB is presented and is shown to be applicable to the EHB. Using an experimentally validated model of BTV, the compensation was performed on a hardware in-the-loop EHB test rig. The preliminary results demonstrate the potential of using an EHB to compensate for brake judder.

  • 319.
    Lee, Chih Feng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Öberg, Per
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Classification of Road Type and Driving Style using OBD Data2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Rollover has for long been a major safety concern for trucks, and will be even more so as automated driving is envisaged to becoming a key element of future mobility. A natural way to address rollover is to extend the capabilities of current active-safety systems with a system that intervenes by steering or braking actuation when there is a risk of rollover. Assessing and predicting the rollover is usually performed using rollover indices calculated either from lateral acceleration or lateral load transfer. Since these indices are evaluated based on different physical observations it is not obvious how they can be compared or how well they reflect rollover events in different situations. <p> In this paper we investigate the implication of the above mentioned rollover indices in different critical maneuvers for a heavy 8x4 twin-steer truck. The analysis is based on optimal control applied to a five degrees of freedom chassis model with individual wheel dynamics and high-fidelity tire-force modeling. Driving scenarios prone to rollover accidents are considered, with a circular-shaped turn and a slalom maneuver being studied in-depth. The optimization objective for the considered maneuvers are formulated as minimum-time and maximum entry-speed problems, both triggering critical maneuvers and forcing the vehicle to operate on the limit of its physical capabilities. The implication of the rollover indices on the optimal trajectories is investigated by constraining the optimal maneuvers with different rollover indices, thus limiting the vehicle’s maneuvering envelope with respect to each rollover index. The resulting optimal trajectories constrained by different rollover indices are compared and analyzed in detail. Additionally, the conservativeness of the indices for assessing the risk of rollovers are discussed.

  • 320.
    Leek, Viktor
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    An Optimal Control Toolbox for MATLAB Based on CasADi2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Many engineering problems are naturally posed as optimal control problems. It may involve moving between two points in the fastest possible way, or to put a satellite into orbit with minimum energy consumption. Many optimal control problems are too difficult to be solved analytically and therefore require the use of numerical methods. The numerical methods that are the most widespread are the so-called direct methods. However, there is one major drawback with these. If the problem is non-convex, the solution is not guaranteed globally optimal, that is, the absolute best, instead it is guaranteed locally optimal, that is the best in its vicinity. To compensate for this, the problem should be solved several times, under different conditions, in order to investigate whether the solution is a good candidate for the global optimum.

    CasADi is a software specifically designed for dynamic optimization. It has gained wide spread in recent years because it provides all the necessary building blocks for dynamic optimization. This has given individual engineers and scientists the ability to independently formulate and solve all sorts of optimal control problems. However, this requires good theoretical knowledge of the necessary numerical methods.

    The advantage of a toolbox, which solves general optimal control problems, is that the underlying numerical methods have been tested and shown to function on optimal control problems with known solutions. This means that the user does not need exhaustive knowledge of the numerical methods involved, but can focus on formulating and solving optimal control problems.

    The main contribution of this thesis is an optimal control toolbox for MATLAB based on CasADi. The toolbox does not require expert knowledge of the numerical methods, but provides an alternative lower level abstraction that allows for more complex problem formulations.

    The toolbox implements two direct methods, direct multiple shooting and direct collocation. This allows a problem formulation with many degrees of freedom. The most important property of the toolbox is that the discretization can be changed, without the problem formulation needing to be altered. This way the user can easily change the conditions for his/her problem.

    The thesis describes how the two implemented direct methods work, and the design choices made. It also describes what remains to test and evaluate, and the problems that have been used as a reference during the development process.

  • 321.
    Leek, Viktor
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Ekberg, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Development and Usage of a Continuously Differentiable Heavy Duty Diesel Engine Model Equipped with VGT and EGR2017Inngår i: SAE Technical Papers 2017-01-0611, SAE International , 2017, artikkel-id 2017-01-0611Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Today’s need for fuel efficient vehicles, together with increasing engine component complexity, makes optimal control a valuable tool in the process of finding the most fuel efficient control strategies. To efficiently calculate the solution to optimal control problems a gradient based optimization technique is desirable, making continuously differentiable models preferable. Many existing control-oriented Diesel engine models do not fully posses this property, often due to signal saturations or discrete conditions. This paper offers a continuously differentiable, mean value engine model, of a heavy-duty diesel engine equipped with VGT and EGR, suitable for optimal control purposes. The model is developed from an existing, validated, engine model, but adapted to be continuously differentiable and therefore tailored for usage in an optimal control environment. The changes due to the conversion are quantified and presented. Furthermore, it is shown and analyzed how to optimally control the engine in a fuel optimal way under steady-state conditions, and in a time optimal way in a tip-in scenario.

  • 322.
    Lembke, Benjamin
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Bearing Diagnosis Using Fault Signal Enhancing Teqniques and Data-driven Classification2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Rolling element bearings are a vital part in many rotating machinery, including vehicles. A defective bearing can be a symptom of other problems in the machinery and is due to a high failure rate. Early detection of bearing defects can therefore help to prevent malfunction which ultimately could lead to a total collapse. The thesis is done in collaboration with Scania that wants a better understanding of how external sensors such as accelerometers, can be used for condition monitoring in their gearboxes.

    Defective bearings creates vibrations with specific frequencies, known as Bearing Characteristic Frequencies, BCF [23]. A key component in the proposed method is based on identification and extraction of these frequencies from vibration signals from accelerometers mounted near the monitored bearing. Three solutions are proposed for automatic bearing fault detection. Two are based on data-driven classification using a set of machine learning methods called Support Vector Machines and one method using only the computed characteristic frequencies from the considered bearing faults. Two types of features are developed as inputs to the data-driven classifiers. One is based on the extracted amplitudes of the BCF and the other on statistical properties from Intrinsic Mode Functions generated by an improved Empirical Mode Decomposition algorithm. In order to enhance the diagnostic information in the vibration signals two pre-processing steps are proposed. Separation of the bearing signal from masking noise are done with the Cepstral Editing Procedure, which removes discrete frequencies from the raw vibration signal. Enhancement of the bearing signal is achieved by band pass filtering and amplitude demodulation. The frequency band is produced by the band selection algorithms Kurtogram and Autogram.

    The proposed methods are evaluated on two large public data sets considering bearing fault classification using accelerometer data, and a smaller data set collected from a Scania gearbox. The produced features achieved significant separation on the public and collected data. Manual detection of the induced defect on the outer race on the bearing from the gearbox was achieved. Due to the small amount of training data the automatic solutions were only tested on the public data sets. Isolation performance of correct bearing and fault mode among multiplebearings were investigated. One of the best trade offs achieved was 76.39 % fault detection rate with 8.33 % false alarm rate. Another was 54.86 % fault detection rate with 0 % false alarm rate.

  • 323.
    Leufven, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Surge and Choke Capable Compressor Model2011Inngår i: Proceedings of the 18th IFAC World Congress, 2011 / [ed] Bittanti, Sergio, Cenedese, Angelo, Zampieri, Sandro, International Federation of Automatic Control (IFAC) , 2011, s. 10653-10658Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A compressor model is developed. It is capable of representing mass flow and pressure characteristic for three different regions: surge, normal operation as well as for when the compressor acts as a restriction, i.e. having a pressure ratio of less than unity. Different submodels are discussed and methods to parametrize the given model structure are given. Both the parametrization and validation are supported extensively by measured data. Dynamic data sets include measurements from engine and surge test stands. The compressor model is further validated against a database of stationary compressor maps. The proposed model is shown to have good agreement with measured data for all regions, without the need for extensive geometric information or data.

  • 324.
    Leufvén, Oskar
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Compressor Modeling for Control of Automotive Two Stage Turbochargers2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There is a demand for increasing efficiency of automotive engines, and one way to achieve this is through downsizing and turbocharging. In the design compromises are made, for example the maximum power of the engine determines the size of the compressor, but since the compressor mass flow range is limited, this affects the torque for low engine speeds. A two stage system, with two different sized turbochargers, reduces this compromise, but the system complexity increases. To handle the complexity, models have come to play a central role where they aid engineers in the design. Models are used in simulation, for design optimization and also in the control synthesis. In all applications it is vital that the models have good descriptive capabilities for the entire operating range studied.

    A novel control oriented compressor model is developed, with good performance in the operating regions relevant for compressors in a two stage system. In addition to the nominal operating regime, also surge, choke and operation at pressure ratios less than unity, are modeled. The model structure can be automatically parametrized using a compressor map, and is based on static functions for low computational cost. A sensitivity analysis, isolating the important characteristics that influence surge transients in an engine is performed, and the gains of a novel surge controller are quantified.

    A compressor map is usually measured in a gas stand, that has different surrounding systems, compared to the application where the compressor is used. A method to automatically determine a turbo map, when the turbo is installed on an engine in an engine test stand is developed. The map can then be used to parametrize the developed compressor model, and effectively create a model parametrized for its intended application.

    An experimental analysis of the applicability of the commonly used correction factors, used for estimating compressor performance when the inlet conditions deviate from nominal, is presented. Correction factors are vital, to e.g. estimate turbocharger performance for driving at high altitude or to analyze second stage compressor performance, where the variations in inlet conditions are large. The experimental campaign uses measurements from an engine test cell and from a gas stand, and shows a small, but clearly measurable trend, with decreasing compressor pressure ratio for decreasing compressor inlet pressure, for points with equal corrected shaft speed and corrected mass flow. A method is developed, enabling measurements to be analyzed with modified corrections. An adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction. A high altitude example is used to quantify the influence of the modified correction.

    Delarbeid
    1. Time to Surge Concept and Surge Control for Acceleration Performance
    Åpne denne publikasjonen i ny fane eller vindu >>Time to Surge Concept and Surge Control for Acceleration Performance
    2008 (engelsk)Inngår i: Proceedings of the 17th IFAC World Congress, 2008 / [ed] Chung, Myung Jin; Misra, Pradeep, International Federation of Automatic Control (IFAC) , 2008, s. 2063-2068Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Surge is a dangerous instability that can occur in compressors. It is avoided using a valve that reduces the compressor pressure. The control of this valve is important for the compressor safety but it also has a direct influence on the acceleration performance. Compressor surge control is investigated by first studying the surge phenomenon in detail. Experimental data from a dynamic compressor flow test bench and surge cycles measured on an engine is used to tune and validate a model capable of describing surge. A concept time to surge is introduced and a sensitivity analysis is performed to isolate the important characteristics that influence surge transients in an engine. It is pointed out that the controller clearly benefits from a feed-forward term due to the small time frames associated with the transition to surge. In the next step this knowledge is used in the design of a novel surge controller. This surge controller is then compared to two other controllers and it is shown that it avoids surge and improves the acceleration performance by delivering both higher engine torque and turbo shaft speed after a gear change.

    sted, utgiver, år, opplag, sider
    International Federation of Automatic Control (IFAC), 2008
    Emneord
    automobile powertrains, engine control, compressor, turbo, system modeling
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-50768 (URN)10.3182/20080706-5-KR-1001.00350 (DOI)978-3-902661-00-5 (ISBN)
    Konferanse
    IFAC World Congress, July 6-11, Seuol, Korea
    Tilgjengelig fra: 2013-04-09 Laget: 2009-10-14 Sist oppdatert: 2018-01-30bibliografisk kontrollert
    2. Engine Test Bench Turbo Mapping
    Åpne denne publikasjonen i ny fane eller vindu >>Engine Test Bench Turbo Mapping
    2010 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    A method for determining turbocharger performance on installations in an engine test bench is developed and investigated. The focus is on the mapping of compressor performance but some attention is also given to the turbine mapping. An analysis of the limits that an engine installation imposes on the reachable points in the compressor map is performed, in particular it shows what corrected flows and pressure ratios can be reached and what these limitations depend on. To be able to span over a larger  region of the corrected flow a throttle before the compressor is suggested and this is also verified in the test bench.

    Turbocharger mapping is a time consuming process and there is a need for a systematic process that can be executed automatically. An engine and test cell control structure that can be used to automate and monitor the measurements by controlling the system to the desired operating points is also proposed.

    In experiments, used for constructing the compressor speed lines, it is virtually impossible to control the turbocharger to the exact corrected speed that is postulated by the speed line. To overcome this two methods that compensate for the deviation between measured speed and the desired speed are proposed and investigated. Detailed data from a gas stand is used to evaluate the measurements compared to those that are generated in the engine test cell installation. The agreements are generally good but there is more noise in the engine data and there are also some small systematic deviations.

    sted, utgiver, år, opplag, sider
    SAE International, 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64337 (URN)10.4271/2010-01-1232 (DOI)
    Konferanse
    SAE 2010 World Congress, April 13-15, Detroit, Michigan, USA
    Tilgjengelig fra: 2011-01-19 Laget: 2011-01-19 Sist oppdatert: 2018-01-30
    3. Parametrization and Validation of a Novel Surge Capable Compressor Model for MVEM using Experimental Data
    Åpne denne publikasjonen i ny fane eller vindu >>Parametrization and Validation of a Novel Surge Capable Compressor Model for MVEM using Experimental Data
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A compressor model is developed. It is capable of representing mass flow and pressure characteristic for three different regions: surge, normal operation as well as for when the compressor acts as a restriction, i.e. having a pressure ratio of less than unity. Different submodels are discussed and methods to parametrize the given model structure are given. Both the parameterization and validation are supported extensively by measured data. Transient data sets include measurements from engine test stands and a surge test stand. The compressor model is further validated against a data base of stationary compressor maps. The proposed model is shown to have good agreement with measured data for all regions, without the need for extensive geometric information or data.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64339 (URN)
    Tilgjengelig fra: 2011-01-19 Laget: 2011-01-19 Sist oppdatert: 2018-01-30bibliografisk kontrollert
    4. Investigation of compressor correction quantities for automotive applications
    Åpne denne publikasjonen i ny fane eller vindu >>Investigation of compressor correction quantities for automotive applications
    2012 (engelsk)Inngår i: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, Vol. 13, nr 6, s. 588-606Artikkel i tidsskrift (Annet vitenskapelig) Published
    Abstract [en]

    Turbo performance is represented using maps, measured for one set of inlet conditions. Corrections are then applied to scale the performance to other inlet conditions. A turbo compressor for automotive applications experiences large variations in inlet conditions, and the use of two stage charging increases these variations. The variations are the motivation for analyzing the correction quantities and their validity. The corrections reveals a novel surge avoidance strategy, where the result is that a reduction in inlet pressure increases the surge margin for eight maps studied. The method to investigate the applicability of the strategy is general.

    An experimental analysis of the applicability of the commonly used correction factors, used when estimating compressor performance for varying inlet conditions, is presented. The experimental campaign uses measurements from an engine test cell and from a gas stand, and shows a small, but clearly measurable trend, with decreasing compressor  pressure ratio for decreasing compressor inlet pressure. A method is  developed, enabling measurements to be analyzed with modified corrections.

    An adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction. The resulting decrease in high altitude engine performance, due to compressor limitations, are quantified and shows a reduction in altitude of 200 – 600 m, for when engine torque has to be reduced to due limited compressor operation.

    sted, utgiver, år, opplag, sider
    SAGE Publications (UK and US) / Professional Engineering Publishing (Institution of Mechanical Engineers), 2012
    Emneord
    Experimental analysis; map; inlet conditions; speed line; measurements
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64340 (URN)10.1177/1468087412439018 (DOI)000311831200004 ()
    Tilgjengelig fra: 2011-01-19 Laget: 2011-01-19 Sist oppdatert: 2018-01-30bibliografisk kontrollert
  • 325.
    Leufvén, Oskar
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Modeling for control of centrifugal compressors2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Downsizing and turbocharging of engines provide a way to meet increasing demands for efficiency and performance in the automotive industry. An engine design is a result of compromises, e.g. the selection of charging system, and the trend is to reduce these compromises by increasing system complexity. Models have come to play a central role to handle this rise in complexity, and are used for simulation, system optimization and control synthesis. The models should describe the entire operating range, be capable of extrapolation, be easily parameterizable, and wide cover a range of applications.

    A novel compressor model is developed which, in addition to the nominal operation, also covers surge, choke and operation at pressure ratios less than one. The model is based on data from more than 300 compressor maps, measurements from engine test stands, and a surge test stand. The general knowledge gained from the in-depth analysis is condensed in the model equations. The model can be automatically parametrized using a compressor map, is based on static functions for low computational cost, and is shown to extrapolate low speed compressor operation well. Furthermore, it is shown to be applicable to compressors of different size, ranging from small car applications to large heavy duty vehicles. Compressor restriction operation is modeled down to a standstill compressor, and shown to agree well with gas stand measurements. Further, the analysis contributes with new knowledge and models for choking pressure ratio and flow.

    A method to automatically determine a turbo map, when the turbo is installed on an engine in an engine test stand is developed. The method can be used to validate manufacturer maps or expand the region covered in a map. An analysis of the limits that an engine installation imposes on the reachable points in the compressor map is performed. The addition of a throttle before the compressor is suggested to increase the reachable map region, and an engine and test cell control structure that can be used to automate the measurements is proposed. Two methods that compensate for the deviation between measured and desired speeds, are proposed and investigated. A gas stand map is compared to the map generated in the engine test stand, and a generally good agreement results.

    An experimental analysis of the applicability of the commonly used correction factors, used for estimating compressor performance when the inlet conditions deviate from nominal, is performed. Correction factors are vital, to e.g. estimate turbocharger performance for driving at high altitude or to characterize second stage compressor performance, where the variations in inlet conditions are large. Measurements from an engine test stand and a gas stand show a small but clearly measurable trend, with decreasing compressor pressure ratio for decreasing compressor inlet pressure, for points with equal corrected shaft speed and corrected mass flow. A method that enables measurements to be analyzed with modified corrections is developed. As a result, an adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction.

    Delarbeid
    1. Time to Surge Concept and Surge Control for Acceleration Performance
    Åpne denne publikasjonen i ny fane eller vindu >>Time to Surge Concept and Surge Control for Acceleration Performance
    2008 (engelsk)Inngår i: Proceedings of the 17th IFAC World Congress, 2008 / [ed] Chung, Myung Jin; Misra, Pradeep, International Federation of Automatic Control (IFAC) , 2008, s. 2063-2068Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Surge is a dangerous instability that can occur in compressors. It is avoided using a valve that reduces the compressor pressure. The control of this valve is important for the compressor safety but it also has a direct influence on the acceleration performance. Compressor surge control is investigated by first studying the surge phenomenon in detail. Experimental data from a dynamic compressor flow test bench and surge cycles measured on an engine is used to tune and validate a model capable of describing surge. A concept time to surge is introduced and a sensitivity analysis is performed to isolate the important characteristics that influence surge transients in an engine. It is pointed out that the controller clearly benefits from a feed-forward term due to the small time frames associated with the transition to surge. In the next step this knowledge is used in the design of a novel surge controller. This surge controller is then compared to two other controllers and it is shown that it avoids surge and improves the acceleration performance by delivering both higher engine torque and turbo shaft speed after a gear change.

    sted, utgiver, år, opplag, sider
    International Federation of Automatic Control (IFAC), 2008
    Emneord
    automobile powertrains, engine control, compressor, turbo, system modeling
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-50768 (URN)10.3182/20080706-5-KR-1001.00350 (DOI)978-3-902661-00-5 (ISBN)
    Konferanse
    IFAC World Congress, July 6-11, Seuol, Korea
    Tilgjengelig fra: 2013-04-09 Laget: 2009-10-14 Sist oppdatert: 2018-01-30bibliografisk kontrollert
    2. Engine Test Bench Turbo Mapping
    Åpne denne publikasjonen i ny fane eller vindu >>Engine Test Bench Turbo Mapping
    2010 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    A method for determining turbocharger performance on installations in an engine test bench is developed and investigated. The focus is on the mapping of compressor performance but some attention is also given to the turbine mapping. An analysis of the limits that an engine installation imposes on the reachable points in the compressor map is performed, in particular it shows what corrected flows and pressure ratios can be reached and what these limitations depend on. To be able to span over a larger  region of the corrected flow a throttle before the compressor is suggested and this is also verified in the test bench.

    Turbocharger mapping is a time consuming process and there is a need for a systematic process that can be executed automatically. An engine and test cell control structure that can be used to automate and monitor the measurements by controlling the system to the desired operating points is also proposed.

    In experiments, used for constructing the compressor speed lines, it is virtually impossible to control the turbocharger to the exact corrected speed that is postulated by the speed line. To overcome this two methods that compensate for the deviation between measured speed and the desired speed are proposed and investigated. Detailed data from a gas stand is used to evaluate the measurements compared to those that are generated in the engine test cell installation. The agreements are generally good but there is more noise in the engine data and there are also some small systematic deviations.

    sted, utgiver, år, opplag, sider
    SAE International, 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64337 (URN)10.4271/2010-01-1232 (DOI)
    Konferanse
    SAE 2010 World Congress, April 13-15, Detroit, Michigan, USA
    Tilgjengelig fra: 2011-01-19 Laget: 2011-01-19 Sist oppdatert: 2018-01-30
    3. Investigation of compressor correction quantities for automotive applications
    Åpne denne publikasjonen i ny fane eller vindu >>Investigation of compressor correction quantities for automotive applications
    2012 (engelsk)Inngår i: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, Vol. 13, nr 6, s. 588-606Artikkel i tidsskrift (Annet vitenskapelig) Published
    Abstract [en]

    Turbo performance is represented using maps, measured for one set of inlet conditions. Corrections are then applied to scale the performance to other inlet conditions. A turbo compressor for automotive applications experiences large variations in inlet conditions, and the use of two stage charging increases these variations. The variations are the motivation for analyzing the correction quantities and their validity. The corrections reveals a novel surge avoidance strategy, where the result is that a reduction in inlet pressure increases the surge margin for eight maps studied. The method to investigate the applicability of the strategy is general.

    An experimental analysis of the applicability of the commonly used correction factors, used when estimating compressor performance for varying inlet conditions, is presented. The experimental campaign uses measurements from an engine test cell and from a gas stand, and shows a small, but clearly measurable trend, with decreasing compressor  pressure ratio for decreasing compressor inlet pressure. A method is  developed, enabling measurements to be analyzed with modified corrections.

    An adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction. The resulting decrease in high altitude engine performance, due to compressor limitations, are quantified and shows a reduction in altitude of 200 – 600 m, for when engine torque has to be reduced to due limited compressor operation.

    sted, utgiver, år, opplag, sider
    SAGE Publications (UK and US) / Professional Engineering Publishing (Institution of Mechanical Engineers), 2012
    Emneord
    Experimental analysis; map; inlet conditions; speed line; measurements
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64340 (URN)10.1177/1468087412439018 (DOI)000311831200004 ()
    Tilgjengelig fra: 2011-01-19 Laget: 2011-01-19 Sist oppdatert: 2018-01-30bibliografisk kontrollert
    4. A surge and choke capable compressor flow model: Validation and extrapolation capability
    Åpne denne publikasjonen i ny fane eller vindu >>A surge and choke capable compressor flow model: Validation and extrapolation capability
    2013 (engelsk)Inngår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 21, nr 12, s. 1871-1883Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Increasingly stringent emissions legislation combined with consumer performance demand, have created the need for complex automotive engines. The control of these complex system rely heavily on control oriented models. Models capable of describing all operating modes of the systems are beneficial, and the models should be easily parametrized and enable extrapolation. A large database of automotive compressor maps is characterized, and used to develop, validate and automatically parametrize a compressor flow model capable of describing reversed flow, normal operation and choke. Measurement data from both an engine test stand, and a surge test stand, is used to parametrize and validate the surge capability of the model. The model is shown to describe all modes of operation with good performance, and also to be able to extrapolate to small turbo speeds. The extrapolation capability is important, since compressor maps are shown to lack information for low speeds, even though they frequently operate there in an engine installation.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-92090 (URN)10.1016/j.conengprac.2013.07.005 (DOI)000329017200023 ()
    Tilgjengelig fra: 2013-05-07 Laget: 2013-05-07 Sist oppdatert: 2018-01-30bibliografisk kontrollert
    5. Measurement, analysis and modeling of compressor flow for low pressure ratios
    Åpne denne publikasjonen i ny fane eller vindu >>Measurement, analysis and modeling of compressor flow for low pressure ratios
    2016 (engelsk)Inngår i: International journal of engine research, ISSN 1468-0874, Vol. 17, nr 2, s. 153-168Artikkel i tidsskrift (Annet vitenskapelig) Published
    Abstract [en]

    Increasingly stringent emissions legislation combined with consumer performance demands, have driven the development of downsized engines with complex turbocharger arrangements. To handle the complexity model-based methods have become a standard tool, and these methods need models that are capable of describing all operating modes of the systems. The models should also be easily parametrized and enable extrapolation. Both single and multiple stage turbo systems can operate with a pressure drop over their compressors, both stationary and transient. The focus here is to develop models that can describe centrifugal compressors that operate both in normal region and restriction region from standstill to maximum speed. The modeling results rely on an analysis of 305 automotive compressor maps, whereof five contain measured restriction operation, and two contain measured standstill characteristic. A standstill compressor is shown to choke at a pressure ratio of approximately 0.5, and the corresponding choking corrected mass flow being approximately 50% of the compressor maximum flow capacity. Both choking pressure ratio and flow are then shown to increase with corrected speed, and the choking pressure ratio is shown to occur at pressure ratios larger than unity for higher speeds. Simple empirical models are proposed and shown to be able to describe high flow and pressure ratios down to choking conditions well. A novel compressor flow model is proposed and validated to capture the high flow asymptote well, for speeds from standstill up to maximum.

    sted, utgiver, år, opplag, sider
    Sage Publications, 2016
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-92091 (URN)10.1177/1468087414562456 (DOI)000368815100001 ()
    Merknad

    Funding agencies: Vinnova Industry Excellence Center: LINK-SIC Linkoping Center for Sensor Informatics and Control

    Vid tiden för disputation förelåg publikationen endast som manuskript

    Tilgjengelig fra: 2013-05-07 Laget: 2013-05-07 Sist oppdatert: 2018-01-30bibliografisk kontrollert
  • 326.
    Leufvén, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    A surge and choke capable compressor flow model: Validation and extrapolation capability2013Inngår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 21, nr 12, s. 1871-1883Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increasingly stringent emissions legislation combined with consumer performance demand, have created the need for complex automotive engines. The control of these complex system rely heavily on control oriented models. Models capable of describing all operating modes of the systems are beneficial, and the models should be easily parametrized and enable extrapolation. A large database of automotive compressor maps is characterized, and used to develop, validate and automatically parametrize a compressor flow model capable of describing reversed flow, normal operation and choke. Measurement data from both an engine test stand, and a surge test stand, is used to parametrize and validate the surge capability of the model. The model is shown to describe all modes of operation with good performance, and also to be able to extrapolate to small turbo speeds. The extrapolation capability is important, since compressor maps are shown to lack information for low speeds, even though they frequently operate there in an engine installation.

  • 327.
    Leufvén, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Engine Test Bench Turbo Mapping2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A method for determining turbocharger performance on installations in an engine test bench is developed and investigated. The focus is on the mapping of compressor performance but some attention is also given to the turbine mapping. An analysis of the limits that an engine installation imposes on the reachable points in the compressor map is performed, in particular it shows what corrected flows and pressure ratios can be reached and what these limitations depend on. To be able to span over a larger  region of the corrected flow a throttle before the compressor is suggested and this is also verified in the test bench.

    Turbocharger mapping is a time consuming process and there is a need for a systematic process that can be executed automatically. An engine and test cell control structure that can be used to automate and monitor the measurements by controlling the system to the desired operating points is also proposed.

    In experiments, used for constructing the compressor speed lines, it is virtually impossible to control the turbocharger to the exact corrected speed that is postulated by the speed line. To overcome this two methods that compensate for the deviation between measured speed and the desired speed are proposed and investigated. Detailed data from a gas stand is used to evaluate the measurements compared to those that are generated in the engine test cell installation. The agreements are generally good but there is more noise in the engine data and there are also some small systematic deviations.

  • 328.
    Leufvén, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Investigation of compressor correction quantities for automotive applications2012Inngår i: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, Vol. 13, nr 6, s. 588-606Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Turbo performance is represented using maps, measured for one set of inlet conditions. Corrections are then applied to scale the performance to other inlet conditions. A turbo compressor for automotive applications experiences large variations in inlet conditions, and the use of two stage charging increases these variations. The variations are the motivation for analyzing the correction quantities and their validity. The corrections reveals a novel surge avoidance strategy, where the result is that a reduction in inlet pressure increases the surge margin for eight maps studied. The method to investigate the applicability of the strategy is general.

    An experimental analysis of the applicability of the commonly used correction factors, used when estimating compressor performance for varying inlet conditions, is presented. The experimental campaign uses measurements from an engine test cell and from a gas stand, and shows a small, but clearly measurable trend, with decreasing compressor  pressure ratio for decreasing compressor inlet pressure. A method is  developed, enabling measurements to be analyzed with modified corrections.

    An adjusted shaft speed correction quantity is proposed, incorporating also the inlet pressure in the shaft speed correction. The resulting decrease in high altitude engine performance, due to compressor limitations, are quantified and shows a reduction in altitude of 200 – 600 m, for when engine torque has to be reduced to due limited compressor operation.

  • 329.
    Leufvén, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Measurement, analysis and modeling of compressor flow for low pressure ratios2016Inngår i: International journal of engine research, ISSN 1468-0874, Vol. 17, nr 2, s. 153-168Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Increasingly stringent emissions legislation combined with consumer performance demands, have driven the development of downsized engines with complex turbocharger arrangements. To handle the complexity model-based methods have become a standard tool, and these methods need models that are capable of describing all operating modes of the systems. The models should also be easily parametrized and enable extrapolation. Both single and multiple stage turbo systems can operate with a pressure drop over their compressors, both stationary and transient. The focus here is to develop models that can describe centrifugal compressors that operate both in normal region and restriction region from standstill to maximum speed. The modeling results rely on an analysis of 305 automotive compressor maps, whereof five contain measured restriction operation, and two contain measured standstill characteristic. A standstill compressor is shown to choke at a pressure ratio of approximately 0.5, and the corresponding choking corrected mass flow being approximately 50% of the compressor maximum flow capacity. Both choking pressure ratio and flow are then shown to increase with corrected speed, and the choking pressure ratio is shown to occur at pressure ratios larger than unity for higher speeds. Simple empirical models are proposed and shown to be able to describe high flow and pressure ratios down to choking conditions well. A novel compressor flow model is proposed and validated to capture the high flow asymptote well, for speeds from standstill up to maximum.

  • 330.
    Leufvén, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Parametrization and Validation of a Novel Surge Capable Compressor Model for MVEM using Experimental DataManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A compressor model is developed. It is capable of representing mass flow and pressure characteristic for three different regions: surge, normal operation as well as for when the compressor acts as a restriction, i.e. having a pressure ratio of less than unity. Different submodels are discussed and methods to parametrize the given model structure are given. Both the parameterization and validation are supported extensively by measured data. Transient data sets include measurements from engine test stands and a surge test stand. The compressor model is further validated against a data base of stationary compressor maps. The proposed model is shown to have good agreement with measured data for all regions, without the need for extensive geometric information or data.

  • 331.
    Leufvén, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Time to Surge Concept and Surge Control for Acceleration Performance2008Inngår i: Proceedings of the 17th IFAC World Congress, 2008 / [ed] Chung, Myung Jin; Misra, Pradeep, International Federation of Automatic Control (IFAC) , 2008, s. 2063-2068Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Surge is a dangerous instability that can occur in compressors. It is avoided using a valve that reduces the compressor pressure. The control of this valve is important for the compressor safety but it also has a direct influence on the acceleration performance. Compressor surge control is investigated by first studying the surge phenomenon in detail. Experimental data from a dynamic compressor flow test bench and surge cycles measured on an engine is used to tune and validate a model capable of describing surge. A concept time to surge is introduced and a sensitivity analysis is performed to isolate the important characteristics that influence surge transients in an engine. It is pointed out that the controller clearly benefits from a feed-forward term due to the small time frames associated with the transition to surge. In the next step this knowledge is used in the design of a novel surge controller. This surge controller is then compared to two other controllers and it is shown that it avoids surge and improves the acceleration performance by delivering both higher engine torque and turbo shaft speed after a gear change.

  • 332.
    Leuhusen, Joakim
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Karlsson, Andreas
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Simulation and synchronization of distributed real-time systems2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Today we are very much dependent on different kinds of real time systems. Usually,a real time system is a system which is interacting with a physical environmentwith sensors or activators. There are many advantages by replacing mechanicalcomponents with electrical ones. For instance, it is usually cheaper and possibleto add new functions to the device without replacing the electronic part, whichwould have been necessary with a mechanical one.The possibility of simulating a distributed system is used throughout the vehi-cle industry. With the simulation of connected sub systems, using modeled busesand real time kernels, one could increase the correctness of the behavior of the sys-tem and consequently decrease the amount of time spent later in the developingprocess.In this master thesis we used modeled CAN-buses and real time models tosimulate the connection and execution time of the systems. The simulation resultsare used to validate the functionality of the distributed system. Additionally, aworst-case response time analysis is made to set timing constraints on the systemto fulfill given deadlines.During the work, different settings of the network are tested to analyze thesystem frequency needed to sustain deadlines and correctness on the network.

  • 333.
    Lind, Simon
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Powertrain modeling for realtime simulation2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The goal of this thesis was to develop a powertrain model of a vehicle and parametrize itusing non-invasive sensors. The non-invasive sensors available were chassis dynamometer,the pedal robot and the vehicle’s on-board diagnostics which was accessed using a scantool. Non-invasive sensors were used so that the vehicle to model can easily be changed. Aparametrization methodology to parametrize the model for a new vehicle was also developedto facilitate the change of vehicle. The powertrain model is for cars with a combustion engineand a manual gearbox.

    The engine model consist of two static maps, a pedal map and an engine map. The pedalmap is created using the fact that a constant pedal position and engine speed gives a constantthrottle position. The engine map is created in similar manner using that a constant throttleposition and engine speed gives a constant engine torque. The engine model also uses a firstorder lag element to model the time delay from a change in pedal position to a change inwheel torque. The driveline model is a rigid driveline model that assumes that the clutch,driveshaft and propeller shaft are stiff.

    The developed parametrization methodology contains information on how to estimate theparameters of the model which are gear ratios, engine and driveline inertias, engine anddriveline losses, engine and pedal maps and the time constant for the time delay.

    The powertrain model was validated component wise, as standalone and integrated intothe vehicle model against data gathered with the help of the chassis dynamometer. For thestandalone and integrated validation the gathered data were for different driving cases, suchas up and down gear-shifting, engine braking and skipping gears. The standalone validationshowed that the model performed well for the presented driving cases and the results hadgood data fit for 3rd gear and higher. However not for 1st and 2nd gear due to problemsin the pedal map. The pedal map was constructed on the assumption that the same pedalposition for all gears gives the same throttle position, which was not always the case. Thiscaused problems in some areas of the engine and pedal maps however in the validation ofthe maps it was shown that the maps for the most part gave good results.

  • 334.
    Lindahl, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Dahlgren, Viktor
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Powertrain Control for Improved Driver Comfort During Automated Gear Shifts2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 335.
    Lindström, Niclas
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    A Framework for Evaluation of Cylinder Balancing Controllers2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 336.
    Ljungqvist, Oskar
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Evestedt, Niclas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Cirillo, Marcello
    Scania Tech Ctr, Sweden.
    Axehill, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Holmer, Olov
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Lattice-based Motion Planning for a General 2-trailer system2017Inngår i: 2017 28TH IEEE INTELLIGENT VEHICLES SYMPOSIUM (IV 2017), IEEE , 2017, s. 819-824Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Motion planning for a general 2-trailer system poses a hard problem for any motion planning algorithm and previous methods have lacked any completeness or optimality guarantees. In this work we present a lattice-based motion planning framework for a general 2-trailer system that is resolution complete and resolution optimal. The solution will satisfy both differential and obstacle imposed constraints and is intended either as a part of an autonomous system or as a driver support system to automatically plan complicated maneuvers in backward and forward motion. The proposed framework relies on a precomputing step that is performed offline to generate a finite set of kinematically feasible motion primitives. These motion primitives are then used to create a regular state lattice that can be searched for a solution using standard graph-search algorithms. To make this graph-search problem tractable for real-time applications a novel parametrization of the reachable state space is proposed where each motion primitive moves the system from and to a selected set of circular equilibrium configurations. The approach is evaluated over three different scenarios and impressive real-time performance is achieved.

  • 337.
    Llamas, Xavier
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Modeling and Control of EGR on Marine Two-Stroke Diesel Engines2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The international marine shipping industry is responsible for the transport of around 90% of the total world trade. Low-speed two-stroke diesel engines usually propel the largest trading ships. This engine type choice is mainly motivated by its high fuel efficiency and the capacity to burn cheap low-quality fuels. To reduce the marine freight impact on the environment, the International Maritime Organization (IMO) has introduced stricter limits on the engine pollutant emissions. One of these new restrictions, named Tier III, sets the maximum NOx emissions permitted. New emission reduction technologies have to be developed to fulfill the Tier III limits on two-stroke engines since adjusting the engine combustion alone is not sufficient. There are several promising technologies to achieve the required NOx reductions, Exhaust Gas Recirculation (EGR) is one of them.  For automotive applications, EGR is a mature technology, and many of the research findings can be used directly in marine applications. However, there are some differences in marine two-stroke engines, which require further development to apply and control EGR.

    The number of available engines for testing EGR controllers on ships and test beds is low due to the recent introduction of EGR. Hence, engine simulation models are a good alternative for developing controllers, and many different engine loading scenarios can be simulated without the high costs of running real engine tests. The primary focus of this thesis is the development and validation of models for two-stroke marine engines with EGR. The modeling follows a Mean Value Engine Model (MVEM) approach, which has a low computational complexity and permits faster than real-time simulations suitable for controller testing. A parameterization process that deals with the low measurement data availability, compared to the available data on automotive engines, is also investigated and described. As a result, the proposed model is parameterized to two different two-stroke engines showing a good agreement with the measurements in both stationary and dynamic conditions.

    Several engine components have been developed. One of these is a new analytic in-cylinder pressure model that captures the influence of the injection and exhaust valve timings without increasing the simulation time. A new compressor model that can extrapolate to low speeds and pressure ratios in a physically sound way is also described. This compressor model is a requirement to be able to simulate low engine loads. Moreover, a novel parameterization algorithm is shown to handle well the model nonlinearities and to obtain a good model agreement with a large number of tested compressor maps. Furthermore, the engine model is complemented with dynamic models for ship and propeller to be able to simulate transient sailing scenarios, where good EGR controller performance is crucial. The model is used to identify the low load area as the most challenging for the controller performance, due to the slower engine air path dynamics. Further low load simulations indicate that sensor bias can be problematic and lead to an undesired black smoke formation, while errors in the parameters of the controller flow estimators are not as critical. This result is valuable because for a newly built engine a proper sensor setup is more straightforward to verify than to get the right parameters for the flow estimators.

    Delarbeid
    1. Parameterizing Compact and Extensible Compressor Models Using Orthogonal Distance Minimization
    Åpne denne publikasjonen i ny fane eller vindu >>Parameterizing Compact and Extensible Compressor Models Using Orthogonal Distance Minimization
    2017 (engelsk)Inngår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 139, nr 1, s. 012601-1-012601-10, artikkel-id GTP-15-1569Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A complete and compact control-oriented compressor model consisting of a mass flow submodel and an efficiency submodel is described. The final application of the model is a complete two-stroke mean value engine model (MVEM) which requires simulating the compressor operating at the low-flow and low-pressure ratio area. The model is based on previous research done for automotive-size compressors, and it is shown to be general enough to adapt well to the characteristics of the marine-size compressors. A physics-based efficiency model allows, together with the mass flow model, extrapolating to low-pressure ratios. The complexity of the model makes its parameterization a difficult task; hence, a method to efficiently estimate the 19 model parameters is proposed. The method computes analytic model gradients and uses them to minimize the orthogonal distances between the modeled speed lines (SpLs) and the measured points. The results of the parameter estimation are tested against nine different standard marine-size maps showing good agreement with the measured data. Furthermore, the results also show the importance of estimating the parameters of the mass flow and efficiency submodels at the same time to obtain an accurate model. The extrapolation capabilities to low-load regions are also tested using low-load measurements from an automotive-size compressor. It is shown that the model follows the measured efficiency trend down to low loads.

    sted, utgiver, år, opplag, sider
    ASME Press, 2017
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-136199 (URN)10.1115/1.4034152 (DOI)000395511600016 ()
    Merknad

    Funding Agencies|European Union [634135]

    Tilgjengelig fra: 2017-04-03 Laget: 2017-04-03 Sist oppdatert: 2019-04-02bibliografisk kontrollert
    2. Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation
    Åpne denne publikasjonen i ny fane eller vindu >>Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation
    2017 (engelsk)Inngår i: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, nr 4Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Downsizing and turbocharging with single or multiple stages has been one of the main solutions to decrease fuel consumption and harmful exhaust emissions, while keeping a sufficient power output. An accurate and reliable control-oriented compressor model can be very helpful during the development phase, as well as for engine calibration, control design, diagnostic purposes or observer design. A complete compressor model consisting of mass flow and efficiency models is developed and motivated. The proposed model is not only able to represent accurately the normal region measured in a compressor map but also it is capable to extrapolate to low compressor speeds. Moreover, the efficiency extrapolation is studied by analyzing the known problem with heat transfer from the hot turbine side, which introduces errors in the measurements done in standard gas stands. Since the parameterization of the model is an important and necessary step in the modeling, a tailored parameterization approach is presented based on Total Least Squares. A standard compressor map is the only data required to parameterize the model. The parameterization is tested with a database of more than 230 compressor maps showing that it can deal well with different compressor sizes and characteristics. Also, general initialization values for the model parameters are provided using the complete database parameterization results. The results show that the model accuracy is good and in general achieves relative errors below one percent. A comparison of the model accuracy for compressor maps with and without heat transfer influence is carried out, showing a similar model accuracy for both cases but better when no heat transfer is present. Furthermore, it is shown that the model is capable to predict the efficiency characteristics at low speed of two compressor maps, measured with near adiabatic conditions.

    sted, utgiver, år, opplag, sider
    United States: S A E Inc., 2017
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-136799 (URN)10.4271/2017-01-1032 (DOI)
    Forskningsfinansiär
    EU, Horizon 2020, 634135
    Tilgjengelig fra: 2017-04-26 Laget: 2017-04-26 Sist oppdatert: 2018-01-30bibliografisk kontrollert
    3. Modeling of a Large Marine Two-Stroke Diesel Engine with Cylinder Bypass Valve and EGR System
    Åpne denne publikasjonen i ny fane eller vindu >>Modeling of a Large Marine Two-Stroke Diesel Engine with Cylinder Bypass Valve and EGR System
    2015 (engelsk)Inngår i: 10th IFAC Conference on Manoeuvring and Control of Marine Craft MCMC 2015: Copenhagen, 24–26 August 2015 / [ed] Roberto Galeazzi and Mogens Blanke, IFAC Papers Online, 2015, Vol. 48, s. 273-278Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    A nonlinear mean value engine model (MVEM) of a two-stroke turbocharged marine diesel engine is developed, parameterized and validated against measurement data. The goal is to have a computationally fast and accurate engine model that captures the main dynamics and can be used in the development of control systems for the newly introduced EGR system. The tuning procedure used is explained, and the result is a six-state MVEM with seven control inputs that capture the main system dynamics.

    sted, utgiver, år, opplag, sider
    IFAC Papers Online, 2015
    Emneord
    Engine modeling, diesel engines, parametrization, validation, nonlinear systems
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-136802 (URN)10.1016/j.ifacol.2015.10.292 (DOI)2-s2.0-84992491352 (Scopus ID)
    Konferanse
    10th IFAC Conference on Manoeuvring and Control of Marine Craft
    Tilgjengelig fra: 2017-04-26 Laget: 2017-04-26 Sist oppdatert: 2018-02-05bibliografisk kontrollert
    4. A Model of a Marine Two-Stroke Diesel Engine with EGR for Low Load Simulation
    Åpne denne publikasjonen i ny fane eller vindu >>A Model of a Marine Two-Stroke Diesel Engine with EGR for Low Load Simulation
    2016 (engelsk)Inngår i: 9th EUROSIM Congress, 2016Konferansepaper, Oral presentation with published abstract (Fagfellevurdert)
    Abstract [en]

    A mean value engine model of a two-stroke ma-rine diesel engine with EGR that is capable of simulatingduring low load operation is developed. In order to beable to perform low load simulations, a compressor modelcapable of low speed extrapolation is also investigated andparameterized for two different compressors. Moreover, aparameterization procedure to get good parameters for bothstationary and dynamic simulations is described and applied.The model is validated for two engine layouts of the same testengine but with different turbocharger units. The simulationresults show a good agreement with the different measuredsignals, including the oxygen content in the scavengingmanifold.

    Emneord
    Modeling, Parameterization, Simulations, Exhaust gas recirculation, Combustion engines
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-136804 (URN)
    Konferanse
    9th EUROSIM Congress on Modelling and Simulation. 12 - 16 September 2016 in Oulu, Finland.
    Forskningsfinansiär
    EU, Horizon 2020, 634135
    Tilgjengelig fra: 2017-04-26 Laget: 2017-04-26 Sist oppdatert: 2018-02-22bibliografisk kontrollert
    5. Control-oriented modeling of two-stroke diesel engines with exhaust gas recirculation for marine applications
    Åpne denne publikasjonen i ny fane eller vindu >>Control-oriented modeling of two-stroke diesel engines with exhaust gas recirculation for marine applications
    2019 (engelsk)Inngår i: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, E-ISSN 2041-3084, Vol. 233, nr 2, s. 551-574Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Large marine two-stroke diesel engines are widely used as propulsion systems for shipping worldwide and are facing stricter NOx emission limits. Exhaust gas recirculation is introduced to these engines to reduce the produced combustion NOx to the allowed levels. Since the current number of engines built with exhaust gas recirculation is low and engine testing is very expensive, a powerful alternative for developing exhaust gas recirculation controllers for such engines is to use control-oriented simulation models. Unfortunately, the same reasons that motivate the use of simulation models also hinder the capacity to obtain sufficient measurement data at different operating points for developing the models. A mean value engine model of a large two-stroke diesel with exhaust gas recirculation that can be simulated faster than real time is presented and validated. An analytic model for the cylinder pressure that captures the effects of changes in the fuel control inputs is also developed and validated with cylinder pressure measurements. A parameterization procedure that deals with the low number of measurement data available is proposed. After the parameterization, the model is shown to capture the stationary operation of the real engine well. The transient prediction capability of the model is also considered satisfactory which is important if the model is to be used for exhaust gas recirculation controller development during transients. Furthermore, the experience gathered while developing the model about essential signals to be measured is summarized, which can be very helpful for future applications of the model. Finally, models for the ship propeller and resistance are also investigated, showing good agreement with the measured ship sailing signals during maneuvers. These models give a complete vessel model and make it possible to simulate various maneuvering scenarios, giving different loading profiles that can be used to investigate the performance of exhaust gas recirculation and other controllers during transients.

    sted, utgiver, år, opplag, sider
    Sage Publications, 2019
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-147828 (URN)10.1177/1475090218768992 (DOI)000470866500011 ()
    Konferanse
    Proceedings of the Institution of Mechanical Engineers
    Merknad

    Funding agencies: European Union [634135]

    Tilgjengelig fra: 2018-05-15 Laget: 2018-05-15 Sist oppdatert: 2019-07-15
  • 338.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    A Model of a Marine Two-Stroke Diesel Engine with EGR for Low Load Simulation2016Inngår i: 9th EUROSIM Congress, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A mean value engine model of a two-stroke ma-rine diesel engine with EGR that is capable of simulatingduring low load operation is developed. In order to beable to perform low load simulations, a compressor modelcapable of low speed extrapolation is also investigated andparameterized for two different compressors. Moreover, aparameterization procedure to get good parameters for bothstationary and dynamic simulations is described and applied.The model is validated for two engine layouts of the same testengine but with different turbocharger units. The simulationresults show a good agreement with the different measuredsignals, including the oxygen content in the scavengingmanifold.

  • 339.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Control-Oriented Compressor Model with Adiabatic Efficiency Extrapolation2017Inngår i: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Downsizing and turbocharging with single or multiple stages has been one of the main solutions to decrease fuel consumption and harmful exhaust emissions, while keeping a sufficient power output. An accurate and reliable control-oriented compressor model can be very helpful during the development phase, as well as for engine calibration, control design, diagnostic purposes or observer design. A complete compressor model consisting of mass flow and efficiency models is developed and motivated. The proposed model is not only able to represent accurately the normal region measured in a compressor map but also it is capable to extrapolate to low compressor speeds. Moreover, the efficiency extrapolation is studied by analyzing the known problem with heat transfer from the hot turbine side, which introduces errors in the measurements done in standard gas stands. Since the parameterization of the model is an important and necessary step in the modeling, a tailored parameterization approach is presented based on Total Least Squares. A standard compressor map is the only data required to parameterize the model. The parameterization is tested with a database of more than 230 compressor maps showing that it can deal well with different compressor sizes and characteristics. Also, general initialization values for the model parameters are provided using the complete database parameterization results. The results show that the model accuracy is good and in general achieves relative errors below one percent. A comparison of the model accuracy for compressor maps with and without heat transfer influence is carried out, showing a similar model accuracy for both cases but better when no heat transfer is present. Furthermore, it is shown that the model is capable to predict the efficiency characteristics at low speed of two compressor maps, measured with near adiabatic conditions.

  • 340.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Control-oriented modeling of two-stroke diesel engines with exhaust gas recirculation for marine applications2019Inngår i: Journal of Engineering for the Maritime Environment (Part M), ISSN 1475-0902, E-ISSN 2041-3084, Vol. 233, nr 2, s. 551-574Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Large marine two-stroke diesel engines are widely used as propulsion systems for shipping worldwide and are facing stricter NOx emission limits. Exhaust gas recirculation is introduced to these engines to reduce the produced combustion NOx to the allowed levels. Since the current number of engines built with exhaust gas recirculation is low and engine testing is very expensive, a powerful alternative for developing exhaust gas recirculation controllers for such engines is to use control-oriented simulation models. Unfortunately, the same reasons that motivate the use of simulation models also hinder the capacity to obtain sufficient measurement data at different operating points for developing the models. A mean value engine model of a large two-stroke diesel with exhaust gas recirculation that can be simulated faster than real time is presented and validated. An analytic model for the cylinder pressure that captures the effects of changes in the fuel control inputs is also developed and validated with cylinder pressure measurements. A parameterization procedure that deals with the low number of measurement data available is proposed. After the parameterization, the model is shown to capture the stationary operation of the real engine well. The transient prediction capability of the model is also considered satisfactory which is important if the model is to be used for exhaust gas recirculation controller development during transients. Furthermore, the experience gathered while developing the model about essential signals to be measured is summarized, which can be very helpful for future applications of the model. Finally, models for the ship propeller and resistance are also investigated, showing good agreement with the measured ship sailing signals during maneuvers. These models give a complete vessel model and make it possible to simulate various maneuvering scenarios, giving different loading profiles that can be used to investigate the performance of exhaust gas recirculation and other controllers during transients.

  • 341.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    LiU CPgui: A Toolbox for Parameterizing Compressor Models2018Rapport (Annet vitenskapelig)
    Abstract [en]

    A toolbox for parameterizing the ellipse model, that is a control-oriented compressor model, to any given measured compressor map is described in detail in this document. The compressor model has been developed in previous publications and shown to be capable of accurately reproducing the measured data obtained from gas stand measurements, for a wide range of compressors, starting from small automotive applications to large compressors used in marine propulsion. In addition, it has been shown that it is possible to extrapolate both mass flow and efficiency to the unmeasured low speed region of the compressor in a physical way. The parameterization algorithm is based on Total Least Squares (TLS), which is shown here and in previous publications to be a fast and reliable approach to fit the compressor model to the map. The toolbox is implemented in a Matlab Graphical User Interface (GUI) in order to make it easy for the user to parameterize the compressor model. To demonstrate the workflow and ease of use, a complete step-by-step example of how to work with the toolbox is provided. To further facilitate the user in applying the model, the package also provides implementations of the ellipse compressor model both as a Matlab function and as a Simulink block. This way, the user can quickly and reliably use the results of the parameterization process in a desired application, e.g. including the compressor model of a given compressor map in a combustion engine simulation model.

  • 342.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Optimal Transient Control of a Heavy DutyDiesel Engine with EGR and VGT2014Inngår i: Proceedings of the 19th IFAC World Congress / [ed] Boje, Edward, Xia, Xiaohua, Cape Town, South Africa: IFAC Papers Online, 2014, Vol. 19, s. 11854-11859Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Optimal control of a heavy duty diesel engine with EGR and VGT during transients is investigated. Minimum time and fuel optimal control problems are defined for transients from low to high output torque. A validated diesel engine model is used with minor changes in order to be suitable for the selected solver. The problem is solved for several feasible minimum EGR fractions and smoke-limiter values in order to provide comparisons. The optimization results show that the smoke-limiter has great effect on the transient duration while the required EGR fraction influences the control signals' shape. The fuel optimal control keeps the control actuators more closed than the time optimal, however both time and fuel optimal results become very similar when high EGR fractions and smoke-limiter values are required.

  • 343.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Parameterizing Compact and Extensible Compressor Models Using Orthogonal Distance Minimization2017Inngår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 139, nr 1, s. 012601-1-012601-10, artikkel-id GTP-15-1569Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A complete and compact control-oriented compressor model consisting of a mass flow submodel and an efficiency submodel is described. The final application of the model is a complete two-stroke mean value engine model (MVEM) which requires simulating the compressor operating at the low-flow and low-pressure ratio area. The model is based on previous research done for automotive-size compressors, and it is shown to be general enough to adapt well to the characteristics of the marine-size compressors. A physics-based efficiency model allows, together with the mass flow model, extrapolating to low-pressure ratios. The complexity of the model makes its parameterization a difficult task; hence, a method to efficiently estimate the 19 model parameters is proposed. The method computes analytic model gradients and uses them to minimize the orthogonal distances between the modeled speed lines (SpLs) and the measured points. The results of the parameter estimation are tested against nine different standard marine-size maps showing good agreement with the measured data. Furthermore, the results also show the importance of estimating the parameters of the mass flow and efficiency submodels at the same time to obtain an accurate model. The extrapolation capabilities to low-load regions are also tested using low-load measurements from an automotive-size compressor. It is shown that the model follows the measured efficiency trend down to low loads.

  • 344.
    Llamas, Xavier
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Sundström, Christofer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Fuel Efficient Speed Profiles for Finite Time Gear Shift with Multi-Phase Optimization2013Inngår i: 54th SIMS Conference on Simulation and Modelling, SIMS 2013, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A method that finds fuel optimal speed profiles for traveling a predefined distance is presented. The vehicle is modeled using a quasistatic formulation and an optimal control problem is defined. In addition, the solving method is based on a multi-phase optimization algorithm based on dynamic programming. This approach results in lower computational time than solving the problem directly with dynamic programming, it also makes the computational time independent of the travel distance. In addition, the simulation generated data can be used to get the solution to several optimal control problems in parallel that have additional constraints. Further a finite time gear shift model is presented to include the gear selection in the optimization problem. The problem also considers speed losses and fuel consumption during the maneuver. The results presented show the optimal speed and gear profiles to cover a distance, making special emphasis at the acceleration phase, where it is optimal to perform a fast acceleration to engage the highest gear as soon as possible. Finally a proposed application is to use the simulation data to provide eco-driving tips to the driver.

  • 345.
    Lockowandt, Karin
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Parsing and Validation of Modelica Models Utilising Fault Diagnosis2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Models have become an indispensable tool within most industrial sectors and are used to reduce costs, enhance the performance of a system etc. The computer support within modelling is extensive, whereof the programming language Modelica is eminent, especially for multi-domain models. Dymola, a commercial program, is built on Modelica and is foremost used for simulation purposes, but many applications for which models are useful are not supported by Dymola. Instead other tools, e.g. Matlab, could be used to exploit the full potential of a model, which means that it first would be needed to be translated. This master's thesis examines one of the possible ways to accomplish this. Specifically the possibility to translate Modelica-models via an XML file, generated by Dymola, is examined. The structure and content of this file is explored, and based thereupon a software is implemented in Python, which successfully translates the models constituting the base for this thesis. Specifically the method was developed on a model of a sub-system of Saab 39 Gripen air-plane.

    Besides porting models between different languages, it is of great interest to determine how well a model describes the system on which it is based. Hence a new method for model validation is developed using the Matlab Fault Diagnosis Toolbox, which also determines the Matlab syntax of the Modelica translation. The novelty with the developed method, compared to traditional model validation methods, is that it is equation based. It is meant to point out specifically which equations are poorly fitted to validation data. On a simple example model the method was successfully used to isolate a poorly fitted equation. This is accomplished by introducing faults to the equations and generating residuals, based on sets of over-determined equations. As a measure of the modelling error the estimation error of the simulated residuals is used, which are weighted together depending on the fault properties of the residuals.

  • 346.
    Lorentzon, Lukas
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Investigation of a troubleshooting procedure: By assessing fault tracing algorithms2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The thesis delves into the area of troubleshooting procedures, an interesting areafor industry. Many products in industry tend to be complex, which in turn makestroubleshooting procedures trickier. A fast and efficient repair process is oftendesired, since customers want the product to be repaired as fast as possible.

    The purpose of a troubleshooting procedure is to find a fault in a broken product,and to choose proper repair actions in a workshop. Such a procedure can besimplified by diagnosis tools, for example software programs that make faultconclusions based on fault codes. These tools can make such conclusions withthe help of algorithms, i.e. fault tracing algorithms.

    Before a product release, it is hard to specify all faults and connections in the system.New unknown fault cases are likely to arise after release, and somehow thisneed to be taken into account in the troubleshooting scenario. The troubleshootingprocedure can be made more robust, if new data could be easily incorporatedin the current structure. This work seek to answer how new data can be incorporatedin trouble shooting procedures.

    A good and reliable fault tracing algorithm is essential in the process of findingfaults and repair actions, which is the reason behind the focus of this thesis. Thepresented problem asks how a fault can be identified from fault codes and symptoms,in order to recommend suitable repair actions. Therefore, the problem isdivided into two parts, finding the fault and recommending repair actions. Inthe first part, three candidate algorithms for finding the faults are investigated,namely Bayesian networks, neural networks, and a method called matrix correlationinspired from latent semantic indexing. The investigation is done by trainingeach algorithm with data, and evaluating the results. The second part consists ofone method proposal for repair action recommendations and one example. Thetheoretical investigation is based on the Servo unit steering (SUS), which residein the IPS system of Volvo Penta.

    The primary contribution of the thesis is the evaluation of three different algorithmsand a proposal of one strategy to recommend suitable repair actions.In this study Bayesian networks are found to conform well with the desired attributes,which in turn lead to the conclusion that Bayesian networks is well suited for this problem.

  • 347.
    Lundahl, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Modeling and Optimization for Critical Vehicle Maneuvers2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    As development in sensor technology, situation awareness systems, and computational hardware for vehicle systems progress, an opportunity for more advanced and sophisticated vehicle safety-systems arises. With the increased level of available information---such as position on the road, road curvature and knowledge about surrounding obstacles---future systems could be seen utilizing more advanced controls, exploiting at-the-limit behavior of the vehicle. Having this in mind, optimization methods have emerged as a powerful tool for offline vehicle-performance evaluation, providing inspiration to new control strategies, and by direct implementation in on-board systems. This will, however, require a careful choice of modeling and objectives, since the solution to the optimization problem will rely on this.

    With emphasis on vehicle modeling for optimization-based maneuvering applications, a vehicle-dynamics testbed has been developed. Using this vehicle in a series of experiments, most extensively in a double lane-change maneuver, verified the functionality and capability of the equipment. Further, a comparative study was performed, considering vehicle models based on the single-track model, extended with, e.g., tire-force saturation, tire-force lag and roll dynamics. The ability to predict vehicle behavior was evaluated against measurement data from the vehicle testbed.

    A platform for solving vehicle-maneuvering optimization-problems has been developed, with state-of-the-art optimization tools, such as JModelica.org and Ipopt. This platform is utilized for studies concerning the influence different vehicle-model configurations have on the solution to critical maneuvering problems. In particular, different tire modeling approaches, as well as vehicle-chassis models of various complexity, are investigated. Also, the influence different road-surface conditions-e.g., asphalt, snow and ice-have on the solution to time-optimal maneuvers is studied.

    The results show that even for less complex models-such as a single-track model with a Magic Formula based tire-model-accurate predictions can be obtained when compared to measurement data. The general observation regarding vehicle modeling for the time-critical maneuvers is similar; even the least complex models can be seen to capture certain characteristics analogous to those of higher complexity.

    Analyzing the results from the optimization problems, it is seen that the overall dynamics, such as resultant forces and yaw moment, obtained for different model configurations, correlates very well. For different road surfaces, the solutions will of course differ due to the various levels of tire-forces being possible to realize. However, remarkably similar vehicle paths are obtained, regardless of surface. These are valuable observations, since they imply that models of less complexity could be utilized in future on-board optimization-algorithms, to generate, e.g., yaw moment and vehicle paths. In combination with additional information from enhanced situation-awareness systems, this enables more advanced safety-systems to be considered for future vehicles.

    Delarbeid
    1. Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
    Åpne denne publikasjonen i ny fane eller vindu >>Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
    2013 (engelsk)Rapport (Annet vitenskapelig)
    Abstract [en]

    For future advanced active safety systems, in road-vehicle applications, there will arise possibilities for enhanced vehicle control systems, due to refinements in, e.g., situation awareness systems. To fully utilize this, more extensive knowledge is required regarding the characteristics and dynamics of vehicle models employed in these systems. Motivated by this, an evaluative study for the lateral dynamics is performed, considering vehicle models of more simple structure. For this purpose, a platform for vehicle dynamics studies has been developed. Experimental data, gathered with this testbed, is then used for model parametrization, succeeded by evaluation for an evasive maneuver. The considered model configurations are based on the single-track model, with different additional attributes, such as tire-force saturation, tire-force lag, and roll dynamics. The results indicate that even a basic model, such as the single-track with tire-force saturation, can describe the lateral dynamics surprisingly well for this critical maneuver.

    sted, utgiver, år, opplag, sider
    Linköping: Linköping University Electronic Press, 2013. s. 22
    Serie
    LiTH-ISY-R, ISSN 1400-3902 ; 3064
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-94203 (URN)LiTH-ISY-R-3064 (ISRN)
    Tilgjengelig fra: 2013-06-18 Laget: 2013-06-18 Sist oppdatert: 2017-01-27bibliografisk kontrollert
    2. Models and Methodology for Optimal Vehicle Maneuvers Applied to a Hairpin Turn
    Åpne denne publikasjonen i ny fane eller vindu >>Models and Methodology for Optimal Vehicle Maneuvers Applied to a Hairpin Turn
    Vise andre…
    2013 (engelsk)Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    There is currently a strongly growing interest in obtaining optimal control solutions for vehicle maneuvers, both in order to understand optimal vehicle behavior and to devise improved safety systems, either by direct deployment of the solutions or by including mimicked driving techniques of professional drivers. However, it is nontrivial to find the right mix of models, formulations, and optimization tools to get useful results for the above purposes. Here, a platform is developed based on a stateof-the-art optimization tool together with adoption of existing vehicle models, where especially the tire models are in focus. A minimum-time formulation is chosen to the purpose of gaining insight in at-the-limit maneuvers, with the overall aim of possibly finding improved principles for future active safety systems. We present optimal maneuvers for different tire models with a common vehicle motion model, and the results are analyzed and discussed. Our main result is that a few-state singletrack model combined with different tire models is able to replicate the behavior of experienced drivers. Further, we show that the different tire models give quantitatively different behavior in the optimal control of the vehicle in the maneuver.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-94204 (URN)
    Konferanse
    The 2013 American Control Conference, June 17-19, Washington, DC, USA
    Tilgjengelig fra: 2013-06-18 Laget: 2013-06-18 Sist oppdatert: 2013-06-18bibliografisk kontrollert
    3. Studying the Influence of Roll and Pitch Dynamics in Optimal Road-Vehicle Maneuvers
    Åpne denne publikasjonen i ny fane eller vindu >>Studying the Influence of Roll and Pitch Dynamics in Optimal Road-Vehicle Maneuvers
    Vise andre…
    2013 (engelsk)Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    A comparative analysis shows how vehicle motion models of different complexity, capturing various characteristics, influence the solution when used in time-critical optimal maneuvering problems. Vehicle models with combinations of roll and pitch dynamics as well as load transfer are considered, ranging from a single-track model to a double-track model with roll and pitch dynamics and load transfer. The optimal maneuvers in a 90◦-turn and a double lane-change scenario are formulated as minimum-time optimization problems, and are solved using numerical optimization software. The results obtained with the different models show that variables potentially important for safety systems, such as the yaw rate, slip angle, and geometric path, are qualitatively the same. Moreover, the numeric differences are mostly within a few percent. The results also indicate that although input torques differ about 50–100 % for certain parts of the maneuver between the most and least complex model considered, the resulting vehicle motions obtained are similar, irrespective of the model. Our main conclusion isthat this enables the use of low-order models when designing the onboard optimization-based safety systems of the future.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-94205 (URN)
    Konferanse
    The 23rd International Symposium on Dynamics of Vehicles on Roads and Tracks, 19-23 August, Qingdao, China
    Tilgjengelig fra: 2013-06-18 Laget: 2013-06-18 Sist oppdatert: 2013-06-18bibliografisk kontrollert
    4. An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions
    Åpne denne publikasjonen i ny fane eller vindu >>An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions
    2013 (engelsk)Inngår i: IFAC Proceedings Volumes, Volume 46, Issue 21, International Federation of Automatic Control , 2013, Vol. 46, s. 66-71Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We investigate optimal maneuvers for road-vehicles on different surfaces such as asphalt, snow, and ice. The study is motivated by the desire to find control strategies for improved future vehicle safety and driver assistance technologies. Based on earlier presented measurements for tire-force characteristics, we develop tire models corresponding to different road conditions, and determine the time-optimal maneuver in a hairpin turn for each of these. The obtained results are discussed and compared for the different road characteristics. Our main findings are that there are fundamental differences in the control strategies on the considered surfaces, and that these differences can be captured with the adopted modeling approach. Moreover, the path of the vehicle center-of-mass was found to be similar for the different cases. We believe that these findings imply that there are observed vehicle behaviors in the results, which can be utilized for developing the vehicle safety systems of tomorrow.

    sted, utgiver, år, opplag, sider
    International Federation of Automatic Control, 2013
    Serie
    IFAC Proceedings Volumes, ISSN 1474-6670 ; Volume 47, Issue 3
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-94206 (URN)10.3182/20130904-4-JP-2042.00007 (DOI)978-3-902823-48-9 (ISBN)
    Konferanse
    7th IFAC Symposium on Advances in Automotive Control. The International Federation of Automatic Control, September 4-7, 2013. Tokyo, Japan
    Tilgjengelig fra: 2013-06-18 Laget: 2013-06-18 Sist oppdatert: 2016-05-25bibliografisk kontrollert
  • 348.
    Lundahl, Kristoffer
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Models and Critical Maneuvers for Road Vehicles2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    As manufacturers are pushing their research and development toward more simulation based and computer aided methods, vehicle dynamics modeling and simulation become more important than ever. The challenge lies in how to utilize the new technology to its fullest, delivering the best possible performance given certain objectives and current restrictions. Here, optimization methods in different forms can be a tremendous asset. However, the solution to an optimization problem will always rely on the problem formulation, where model validity plays a crucial role. The main emphasis in this thesis lies within methodology and analysis of optimal control oriented topics for safety-critical road-vehicle maneuvers. A crucial element here is the vehicle models. This is investigated as a first study, evaluating the degree to which different model configurations can represent the lateral vehicle dynamics in critical maneuvers, where it is shown that even the low-complexity models describe the most essential vehicle characteristics surprisingly well.

    How to formulate the optimization problems and utilize optimal control tools is not obvious. Therefore, a methodology for road-vehicle maneuvering in safety-critical driving scenarios is presented, and used in evaluation studies of various vehicle model configurations and different road-surface conditions. It was found that the overall dynamics is described similarly for both the high- and low-complexity models, as well as for various road-surface conditions.

    If more information about the surroundings is available, the best control actions might differ from the ones in traditional safety systems. This is also studied, where the fundamental control strategies of classic electronic stability control is compared to the optimal strategy in a safety-critical scenario. It is concluded that the optimal braking strategy not only differs from the traditional strategies, but actually counteracts the fundamental intentions from which the traditional systems are based on.

    In contrast to passenger cars, heavy trucks experience other characteristics due to the different geometric proportions. Rollover is one example, which has to be considered in critical maneuvering. Model configurations predicting this phenomenon are investigated using optimal control methods. The results show that the simple first go-to models have to be constrained very conservatively to prevent rollover in more rapid maneuvers.

    In vehicle systems designed for path following, which has become a trending topic with the expanding area of automated driving, the requirements on vehicle modeling can be very high. These requirements ultimately depend on several various properties, where the path restrictions and path characteristics are very influential factors. The interplay between these path properties and the required model characteristics is here investigated. In situations where a smooth path is obtained, low-complexity models can suffice if path deviation tolerances are set accordingly. In more rapid and tricky maneuvers, however, vehicle properties such as yaw inertia are found to be important.

    Several of the included studies indicate that vehicle models of lower complexity can describe the overall dynamics sufficiently in critical driving scenarios, which is a valuable observation for future development.

    Delarbeid
    1. Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
    Åpne denne publikasjonen i ny fane eller vindu >>Vehicle dynamics platform, experiments, and modeling aiming at critical maneuver handling
    2013 (engelsk)Rapport (Annet vitenskapelig)
    Abstract [en]

    For future advanced active safety systems, in road-vehicle applications, there will arise possibilities for enhanced vehicle control systems, due to refinements in, e.g., situation awareness systems. To fully utilize this, more extensive knowledge is required regarding the characteristics and dynamics of vehicle models employed in these systems. Motivated by this, an evaluative study for the lateral dynamics is performed, considering vehicle models of more simple structure. For this purpose, a platform for vehicle dynamics studies has been developed. Experimental data, gathered with this testbed, is then used for model parametrization, succeeded by evaluation for an evasive maneuver. The considered model configurations are based on the single-track model, with different additional attributes, such as tire-force saturation, tire-force lag, and roll dynamics. The results indicate that even a basic model, such as the single-track with tire-force saturation, can describe the lateral dynamics surprisingly well for this critical maneuver.

    sted, utgiver, år, opplag, sider
    Linköping: Linköping University Electronic Press, 2013. s. 22
    Serie
    LiTH-ISY-R, ISSN 1400-3902 ; 3064
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-94203 (URN)LiTH-ISY-R-3064 (ISRN)
    Tilgjengelig fra: 2013-06-18 Laget: 2013-06-18 Sist oppdatert: 2017-01-27bibliografisk kontrollert
    2. Models and methodology for optimal trajectory generation in safety-critical road-vehicle manoeuvres
    Åpne denne publikasjonen i ny fane eller vindu >>Models and methodology for optimal trajectory generation in safety-critical road-vehicle manoeuvres
    2014 (engelsk)Inngår i: Vehicle System Dynamics, ISSN 0042-3114, E-ISSN 1744-5159, Vol. 52, nr 10, s. 1304-1332Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    There is currently a strongly growing interest in obtaining optimal control solutions for vehicle manoeuvres, both in order to understand optimal vehicle behaviour and, perhaps more importantly, to devise improved safety systems, either by direct deployment of the solutions or by including mimicked driving techniques of professional drivers. However, it is non-trivial to find the right combination of models, optimisation criteria, and optimisation tools to get useful results for the above purposes. Here, a platform for investigation of these aspects is developed based on a state-of-the-art optimisation tool together with adoption of existing vehicle chassis and tyre models. A minimum-time optimisation criterion is chosen for the purpose of gaining an insight into at-the-limit manoeuvres, with the overall aim of finding improved fundamental principles for future active safety systems. The proposed method to trajectory generation is evaluated in time-manoeuvres using vehicle models established in the literature. We determine the optimal control solutions for three manoeuvres using tyre and chassis models of different complexities. The results are extensively analysed and discussed. Our main conclusion is that the tyre model has a fundamental influence on the resulting control inputs. Also, for some combinations of chassis and tyre models, inherently different behaviour is obtained. However, certain variables important in vehicle safety-systems, such as the yaw moment and the body-slip angle, are similar for several of the considered model configurations in aggressive manoeuvring situations.

    sted, utgiver, år, opplag, sider
    Taylor andamp; Francis: STM, Behavioural Science and Public Health Titles, 2014
    Emneord
    optimal manoeuvres; time-optimal trajectory generation; road vehicles; chassis and tyre modelling
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-111629 (URN)10.1080/00423114.2014.939094 (DOI)000342291200005 ()
    Merknad

    Funding Agencies|ELLIIT, the Strategic Area for ICT research - Swedish Government; Swedish Research Council

    Tilgjengelig fra: 2014-10-27 Laget: 2014-10-27 Sist oppdatert: 2017-12-05
    3. An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions
    Åpne denne publikasjonen i ny fane eller vindu >>An Investigation of Optimal Vehicle Maneuvers for Different Road Conditions
    2013 (engelsk)Inngår i: IFAC Proceedings Volumes, Volume 46, Issue 21, International Federation of Automatic Control , 2013, Vol. 46, s. 66-71Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We investigate optimal maneuvers for road-vehicles on different surfaces such as asphalt, snow, and ice. The study is motivated by the desire to find control strategies for improved future vehicle safety and driver assistance technologies. Based on earlier presented measurements for tire-force characteristics, we develop tire models corresponding to different road conditions, and determine the time-optimal maneuver in a hairpin turn for each of these. The obtained results are discussed and compared for the different road characteristics. Our main findings are that there are fundamental differences in the control strategies on the considered surfaces, and that these differences can be captured with the adopted modeling approach. Moreover, the path of the vehicle center-of-mass was found to be similar for the different cases. We believe that these findings imply that there are observed vehicle behaviors in the results, which can be utilized for developing the vehicle safety systems of tomorrow.

    sted, utgiver, år, opplag, sider
    International Federation of Automatic Control, 2013
    Serie
    IFAC Proceedings Volumes, ISSN 1474-6670 ; Volume 47, Issue 3
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-94206 (URN)10.3182/20130904-4-JP-2042.00007 (DOI)978-3-902823-48-9 (ISBN)
    Konferanse
    7th IFAC Symposium on Advances in Automotive Control. The International Federation of Automatic Control, September 4-7, 2013. Tokyo, Japan
    Tilgjengelig fra: 2013-06-18 Laget: 2013-06-18 Sist oppdatert: 2016-05-25bibliografisk kontrollert
    4. Towards Lane-Keeping Electronic Stability Control for Road-Vehicles
    Åpne denne publikasjonen i ny fane eller vindu >>Towards Lane-Keeping Electronic Stability Control for Road-Vehicles
    Vise andre…
    2014 (engelsk)Inngår i: Proceedings of the 19th IFAC World Congress, 2014 / [ed] Boje, Edward, Xia, Xiaohua, International Federation of Automatic Control , 2014, Vol. 19, s. 6319-6325Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    The emerging new idea of lane-keeping electronic stability control is investigated. In a critical situation, such as entering a road curve at excessive speed, the optimal behavior may differ from the behavior of traditional ESC, for example, by prioritizing braking over steering response. The important question that naturally arises is if this has a significant effect on safety. The main contribution here is to give a method for some first quantitative measures of this. It is based on optimal control, applied to a double-track chassis model with wheel dynamics and high-fidelity tire-force modeling. The severity of accidents grows with the square of the kinetic energy for high velocities, so using kinetic energy as a measure will at least not overestimate the usefulness of the new safety system principle. The main result is that the safety gain is significant compared to traditional approaches based on yaw rotation, for several situations and different road-condition parameters.

    sted, utgiver, år, opplag, sider
    International Federation of Automatic Control, 2014
    Serie
    World Congress, ISSN 1474-6670 ; Volume 19, Issue 1
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-127795 (URN)10.3182/20140824-6-ZA-1003.02578 (DOI)
    Konferanse
    19th IFAC World Congress, August 24-28, Cape Town, South Africa
    Tilgjengelig fra: 2016-05-12 Laget: 2016-05-12 Sist oppdatert: 2016-05-25bibliografisk kontrollert
    5. Analyzing Rollover Indices for Critical Truck Maneuvers
    Åpne denne publikasjonen i ny fane eller vindu >>Analyzing Rollover Indices for Critical Truck Maneuvers
    2015 (engelsk)Inngår i: SAE International Journal of Commercial Vehicles, ISSN 1946-391X, E-ISSN 1946-3928, Vol. 8, nr 1, s. 189-196Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Rollover has for long been a major safety concern for trucks, and will be even more so as automated driving is envisaged to becoming a key element of future mobility. A natural way to address rollover is to extend the capabilities of current active-safety systems with a system that intervenes by steering or braking actuation when there is a risk of rollover. Assessing and predicting the rollover is usually performed using rollover indices calculated either from lateral acceleration or lateral load transfer. Since these indices are evaluated based on different physical observations it is not obvious how they can be compared or how well they reflect rollover events in different situations.

    In this paper we investigate the implication of the above mentioned rollover indices in different critical maneuvers for a heavy 8×4 twin-steer truck. The analysis is based on optimal control applied to a five degrees of freedom chassis model with individual wheel dynamics and high-fidelity tire-force modeling. Driving scenarios prone to rollover accidents are considered, with a circular-shaped turn and a slalom maneuver being studied in-depth. The optimization objective for the considered maneuvers are formulated as minimum-time and maximum entry-speed problems, both triggering critical maneuvers and forcing the vehicle to operate on the limit of its physical capabilities. The implication of the rollover indices on the optimal trajectories is investigated by constraining the optimal maneuvers with different rollover indices, thus limiting the vehicle's maneuvering envelope with respect to each rollover index. The resulting optimal trajectories constrained by different rollover indices are compared and analyzed in detail. Additionally, the conservativeness of the indices for assessing the risk of rollovers are discussed.

    sted, utgiver, år, opplag, sider
    SAE International, 2015
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-127796 (URN)10.4271/2015-01-1595 (DOI)
    Tilgjengelig fra: 2016-05-12 Laget: 2016-05-12 Sist oppdatert: 2017-11-30bibliografisk kontrollert
    6. Implications of Path Tolerance and Path Characteristics on Critical Vehicle Maneuvers
    Åpne denne publikasjonen i ny fane eller vindu >>Implications of Path Tolerance and Path Characteristics on Critical Vehicle Maneuvers
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Path planning and path following are core components in safe autonomous driving. Typically a path planner provides a path with sometolerance on how tightly the path should be followed. Based on that, and other path characteristics, for example sharpness of curves, a speed profile needs to be assigned so that the vehicle can stay within the given tolerance without going unnecessarily slow. Here, such trajectory planning is based on optimal control formulations where critical cases arises as on-the-limit solutions. Several results are obtained on required model complexity depending on path characteristics, for example quantification of required path tolerance for a simple model to be sufficient, quantification of when yaw inertia needs to be considered in more detail, and how the curvature rate of change of curvature interplays with available friction. Overall, in situations where the path planner, due to the type of vehicle operation ranging from good transport roads to more tricky maneuvering, give paths with a wide range of tolerances and characteristics, then the results provided give the basis for real-time path following with reasonably high speed.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-127797 (URN)
    Tilgjengelig fra: 2016-05-12 Laget: 2016-05-12 Sist oppdatert: 2016-05-25bibliografisk kontrollert
  • 349.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Berntorp, Karl
    Department of Automatic Control, Lund University, Lund, Sweden.
    Olofsson, Björn
    Department of Automatic Control, Lund University, Lund, Sweden.
    Åslund, Jan
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Studying the Influence of Roll and Pitch Dynamics in Optimal Road-Vehicle Maneuvers2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A comparative analysis shows how vehicle motion models of different complexity, capturing various characteristics, influence the solution when used in time-critical optimal maneuvering problems. Vehicle models with combinations of roll and pitch dynamics as well as load transfer are considered, ranging from a single-track model to a double-track model with roll and pitch dynamics and load transfer. The optimal maneuvers in a 90◦-turn and a double lane-change scenario are formulated as minimum-time optimization problems, and are solved using numerical optimization software. The results obtained with the different models show that variables potentially important for safety systems, such as the yaw rate, slip angle, and geometric path, are qualitatively the same. Moreover, the numeric differences are mostly within a few percent. The results also indicate that although input torques differ about 50–100 % for certain parts of the maneuver between the most and least complex model considered, the resulting vehicle motions obtained are similar, irrespective of the model. Our main conclusion isthat this enables the use of low-order models when designing the onboard optimization-based safety systems of the future.

  • 350.
    Lundahl, Kristoffer
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Frisk, Erik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Nielsen, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska fakulteten.
    Implications of Path Tolerance and Path Characteristics on Critical Vehicle ManeuversManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Path planning and path following are core components in safe autonomous driving. Typically a path planner provides a path with sometolerance on how tightly the path should be followed. Based on that, and other path characteristics, for example sharpness of curves, a speed profile needs to be assigned so that the vehicle can stay within the given tolerance without going unnecessarily slow. Here, such trajectory planning is based on optimal control formulations where critical cases arises as on-the-limit solutions. Several results are obtained on required model complexity depending on path characteristics, for example quantification of required path tolerance for a simple model to be sufficient, quantification of when yaw inertia needs to be considered in more detail, and how the curvature rate of change of curvature interplays with available friction. Overall, in situations where the path planner, due to the type of vehicle operation ranging from good transport roads to more tricky maneuvering, give paths with a wide range of tolerances and characteristics, then the results provided give the basis for real-time path following with reasonably high speed.

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